diff --git a/datashuttle/datashuttle_class.py b/datashuttle/datashuttle_class.py
index 267990c82..868df4f02 100644
--- a/datashuttle/datashuttle_class.py
+++ b/datashuttle/datashuttle_class.py
@@ -26,6 +26,7 @@
         OverwriteExistingFiles,
         Prefix,
         TopLevelFolder,
+        TransferErrors,
     )
 
 import yaml
@@ -315,7 +316,8 @@ def upload_custom(
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
         init_log: bool = True,
-    ) -> None:
+        display_errors: bool = True,
+    ) -> TransferErrors:
         """Upload data from a local project to the central project folder.
 
         Parameters
@@ -354,13 +356,16 @@ def upload_custom(
             always be ``True``, unless logger is handled elsewhere
             (e.g. in a calling function).
 
+        display_errors
+            if `True`, a summary of errors will be printed alongside the Rclone logs.
+
         """
         if init_log:
             self._start_log("upload-custom", local_vars=locals())
 
         self._check_top_level_folder(top_level_folder)
 
-        TransferData(
+        errors = TransferData(
             self.cfg,
             "upload",
             top_level_folder,
@@ -369,12 +374,16 @@ def upload_custom(
             datatype,
             overwrite_existing_files,
             dry_run,
-            log=True,
-        )
+        ).run()
+
+        if display_errors:
+            rclone.log_rclone_copy_errors_api(errors)
 
         if init_log:
             ds_logger.close_log_filehandler()
 
+        return errors
+
     @check_configs_set
     @check_is_not_local_project
     def download_custom(
@@ -386,7 +395,8 @@ def download_custom(
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
         init_log: bool = True,
-    ) -> None:
+        display_errors: bool = True,
+    ) -> TransferErrors:
         """Download data from the central project to the local project folder.
 
         Parameters
@@ -425,13 +435,16 @@ def download_custom(
             always be ``True``, unless logger is handled elsewhere
             (e.g. in a calling function).
 
+        display_errors
+            if `True`, a summary of errors will be printed alongside the Rclone logs.
+
         """
         if init_log:
             self._start_log("download-custom", local_vars=locals())
 
         self._check_top_level_folder(top_level_folder)
 
-        TransferData(
+        errors = TransferData(
             self.cfg,
             "download",
             top_level_folder,
@@ -440,12 +453,16 @@ def download_custom(
             datatype,
             overwrite_existing_files,
             dry_run,
-            log=True,
-        )
+        ).run()
+
+        if display_errors:
+            rclone.log_rclone_copy_errors_api(errors)
 
         if init_log:
             ds_logger.close_log_filehandler()
 
+        return errors
+
     # Specific top-level folder
     # ----------------------------------------------------------------------------------
     # A set of convenience functions are provided to abstract
@@ -457,7 +474,7 @@ def upload_rawdata(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Upload all files in the `rawdata` top level folder.
 
         Parameters
@@ -474,7 +491,7 @@ def upload_rawdata(
             transfer was taking place, but no files will be moved.
 
         """
-        self._transfer_top_level_folder(
+        return self._transfer_top_level_folder(
             "upload",
             "rawdata",
             overwrite_existing_files=overwrite_existing_files,
@@ -487,7 +504,7 @@ def upload_derivatives(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Upload all files in the `derivatives` top level folder.
 
         Parameters
@@ -504,7 +521,7 @@ def upload_derivatives(
             transfer was taking place, but no files will be moved.
 
         """
-        self._transfer_top_level_folder(
+        return self._transfer_top_level_folder(
             "upload",
             "derivatives",
             overwrite_existing_files=overwrite_existing_files,
@@ -517,7 +534,7 @@ def download_rawdata(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Download all files in the `rawdata` top level folder.
 
         Parameters
@@ -534,7 +551,7 @@ def download_rawdata(
             transfer was taking place, but no files will be moved..
 
         """
-        self._transfer_top_level_folder(
+        return self._transfer_top_level_folder(
             "download",
             "rawdata",
             overwrite_existing_files=overwrite_existing_files,
@@ -547,7 +564,7 @@ def download_derivatives(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Download all files in the `derivatives` top level folder.
 
         Parameters
@@ -564,7 +581,7 @@ def download_derivatives(
             transfer was taking place, but no files will be moved.
 
         """
-        self._transfer_top_level_folder(
+        return self._transfer_top_level_folder(
             "download",
             "derivatives",
             overwrite_existing_files=overwrite_existing_files,
@@ -577,7 +594,7 @@ def upload_entire_project(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Upload the entire project.
 
         Includes every top level folder (e.g. ``rawdata``, ``derivatives``).
@@ -597,18 +614,21 @@ def upload_entire_project(
 
         """
         self._start_log("upload-entire-project", local_vars=locals())
-        self._transfer_entire_project(
+
+        errors = self._transfer_entire_project(
             "upload", overwrite_existing_files, dry_run
         )
         ds_logger.close_log_filehandler()
 
+        return errors
+
     @check_configs_set
     @check_is_not_local_project
     def download_entire_project(
         self,
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Download the entire project.
 
         Includes every top level folder (e.g. ``rawdata``, ``derivatives``).
@@ -628,11 +648,15 @@ def download_entire_project(
 
         """
         self._start_log("download-entire-project", local_vars=locals())
-        self._transfer_entire_project(
+
+        errors = self._transfer_entire_project(
             "download", overwrite_existing_files, dry_run
         )
+
         ds_logger.close_log_filehandler()
 
+        return errors
+
     @check_configs_set
     @check_is_not_local_project
     def upload_specific_folder_or_file(
@@ -640,7 +664,7 @@ def upload_specific_folder_or_file(
         filepath: Union[str, Path],
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Upload a specific file or folder.
 
         If transferring a single file, the path including the filename is
@@ -666,12 +690,14 @@ def upload_specific_folder_or_file(
         """
         self._start_log("upload-specific-folder-or-file", local_vars=locals())
 
-        self._transfer_specific_file_or_folder(
+        errors = self._transfer_specific_file_or_folder(
             "upload", filepath, overwrite_existing_files, dry_run
         )
 
         ds_logger.close_log_filehandler()
 
+        return errors
+
     @check_configs_set
     @check_is_not_local_project
     def download_specific_folder_or_file(
@@ -679,7 +705,7 @@ def download_specific_folder_or_file(
         filepath: Union[str, Path],
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
-    ) -> None:
+    ) -> TransferErrors:
         """Download a specific file or folder.
 
         If transferring a single file, the path including the filename is
@@ -708,12 +734,14 @@ def download_specific_folder_or_file(
             "download-specific-folder-or-file", local_vars=locals()
         )
 
-        self._transfer_specific_file_or_folder(
+        errors = self._transfer_specific_file_or_folder(
             "download", filepath, overwrite_existing_files, dry_run
         )
 
         ds_logger.close_log_filehandler()
 
+        return errors
+
     def _transfer_top_level_folder(
         self,
         upload_or_download: Literal["upload", "download"],
@@ -721,7 +749,8 @@ def _transfer_top_level_folder(
         overwrite_existing_files: OverwriteExistingFiles = "never",
         dry_run: bool = False,
         init_log: bool = True,
-    ) -> None:
+        display_errors: bool = True,
+    ) -> TransferErrors:
         """Upload or download files within a particular top-level-folder.
 
         A centralised function to upload or download data within
@@ -738,7 +767,7 @@ def _transfer_top_level_folder(
             else self.download_custom
         )
 
-        transfer_func(
+        errors = transfer_func(
             top_level_folder,
             "all",
             "all",
@@ -746,14 +775,17 @@ def _transfer_top_level_folder(
             overwrite_existing_files=overwrite_existing_files,
             dry_run=dry_run,
             init_log=False,
+            display_errors=display_errors,
         )
 
         if init_log:
             ds_logger.close_log_filehandler()
 
+        return errors
+
     def _transfer_specific_file_or_folder(
         self, upload_or_download, filepath, overwrite_existing_files, dry_run
-    ) -> None:
+    ) -> TransferErrors:
         """Core function for upload/download_specific_folder_or_file()."""
         if isinstance(filepath, str):
             filepath = Path(filepath)
@@ -784,6 +816,7 @@ def _transfer_specific_file_or_folder(
             processed_filepath = filepath
 
         include_list = [f"--include /{processed_filepath.as_posix()}"]
+
         output = rclone.transfer_data(
             self.cfg,
             upload_or_download,
@@ -793,8 +826,13 @@ def _transfer_specific_file_or_folder(
                 overwrite_existing_files, dry_run
             ),
         )
+        stdout, stderr, errors = rclone.parse_rclone_copy_output(
+            top_level_folder, output
+        )
+        rclone.log_stdout_stderr_python_api(stdout, stderr)
+        rclone.log_rclone_copy_errors_api(errors)
 
-        utils.log(output.stderr.decode("utf-8"))
+        return errors
 
     # -------------------------------------------------------------------------
     # SSH
@@ -1434,23 +1472,40 @@ def _transfer_entire_project(
         upload_or_download: Literal["upload", "download"],
         overwrite_existing_files: OverwriteExistingFiles,
         dry_run: bool,
-    ) -> None:
+    ) -> TransferErrors:
         """Transfer the entire project.
 
         i.e. every 'top level folder' (e.g. 'rawdata', 'derivatives').
         See ``upload_custom()`` or ``download_custom()`` for parameters.
         """
+        all_errors = rclone.get_empty_errors_dict()
+
         for top_level_folder in canonical_folders.get_top_level_folders():
-            utils.log_and_message(f"Transferring `{top_level_folder}`")
+            utils.log_and_message(
+                f"\n\n*************************************\n"
+                f"Transferring `{top_level_folder}`\n"
+                f"*************************************\n"
+            )
 
-            self._transfer_top_level_folder(
+            errors = self._transfer_top_level_folder(
                 upload_or_download,
                 top_level_folder,
                 overwrite_existing_files=overwrite_existing_files,
                 dry_run=dry_run,
                 init_log=False,
+                display_errors=False,
             )
 
+            all_errors["file_names"] += errors["file_names"]
+            all_errors["messages"] += errors["messages"]
+
+            key = f"nothing_was_transferred_{top_level_folder}"
+            all_errors[key] = errors[key]  # type: ignore
+
+        rclone.log_rclone_copy_errors_api(all_errors)
+
+        return all_errors
+
     def _start_log(
         self,
         command_name: str,
diff --git a/datashuttle/tui/css/tui_menu.tcss b/datashuttle/tui/css/tui_menu.tcss
index b3f8b915b..b795d355d 100644
--- a/datashuttle/tui/css/tui_menu.tcss
+++ b/datashuttle/tui/css/tui_menu.tcss
@@ -91,11 +91,6 @@ MessageBox {
     align: center middle;
 }
 
-#messagebox_top_container {
-    height: 15;
-    width: 65;
- }
-
 #messagebox_message_container {
     align: center middle;
     overflow: hidden auto;
@@ -112,6 +107,8 @@ MessageBox {
     height: 3;
 }
 
+/* NOTE: `messagebox_top_container` width and height are defined on the `MessageBox` class.
+
 /* Light Mode Error Screen */
 
 MessageBox:light > #messagebox_top_container {
diff --git a/datashuttle/tui/interface.py b/datashuttle/tui/interface.py
index 00f6e0697..cc5be7a78 100644
--- a/datashuttle/tui/interface.py
+++ b/datashuttle/tui/interface.py
@@ -259,20 +259,20 @@ def transfer_entire_project(self, upload: bool) -> InterfaceOutput:
             else:
                 transfer_func = self.project.download_entire_project
 
-            transfer_func(
+            errors = transfer_func(
                 overwrite_existing_files=self.tui_settings[
                     "overwrite_existing_files"
                 ],
                 dry_run=self.tui_settings["dry_run"],
             )
 
-            return True, None
+            return True, errors
 
         except BaseException as e:
             return False, str(e)
 
     def transfer_top_level_only(
-        self, selected_top_level_folder: str, upload: bool
+        self, selected_top_level_folder: TopLevelFolder, upload: bool
     ) -> InterfaceOutput:
         """Transfer all files within a selected top level folder.
 
@@ -302,14 +302,14 @@ def transfer_top_level_only(
                     else self.project.download_derivatives
                 )
 
-            transfer_func(
+            errors = transfer_func(
                 overwrite_existing_files=self.tui_settings[
                     "overwrite_existing_files"
                 ],
                 dry_run=self.tui_settings["dry_run"],
             )
 
-            return True, None
+            return True, errors
 
         except BaseException as e:
             return False, str(e)
@@ -349,7 +349,7 @@ def transfer_custom_selection(
             else:
                 transfer_func = self.project.download_custom
 
-            transfer_func(
+            errors = transfer_func(
                 selected_top_level_folder,
                 sub_names=sub_names,
                 ses_names=ses_names,
@@ -360,7 +360,7 @@ def transfer_custom_selection(
                 dry_run=self.tui_settings["dry_run"],
             )
 
-            return True, None
+            return True, errors
 
         except BaseException as e:
             return False, str(e)
diff --git a/datashuttle/tui/screens/modal_dialogs.py b/datashuttle/tui/screens/modal_dialogs.py
index 0d4c94c57..9fb48b244 100644
--- a/datashuttle/tui/screens/modal_dialogs.py
+++ b/datashuttle/tui/screens/modal_dialogs.py
@@ -49,7 +49,13 @@ class MessageBox(ModalScreen):
 
     """
 
-    def __init__(self, message: str, border_color: str) -> None:
+    def __init__(
+        self,
+        message: str,
+        border_color: str,
+        width: str = "65",
+        height: str = "15",
+    ) -> None:
         """Initialise the MessageBox.
 
         Parameters
@@ -60,15 +66,23 @@ def __init__(self, message: str, border_color: str) -> None:
         border_color
             Color of the MessageBox border (e.g. green if the message is positive).
 
+        height
+            The height of the messagebox.
+
+        width
+            The width of the messagebox.
+
         """
         super(MessageBox, self).__init__()
 
         self.message = message
         self.border_color = border_color
+        self.top_container_width = width
+        self.top_container_height = height
 
     def compose(self) -> ComposeResult:
         """Add widgets to the MessageBox."""
-        yield Container(
+        self.top_container = Container(
             Container(
                 Static(self.message, id="messagebox_message_label"),
                 id="messagebox_message_container",
@@ -77,6 +91,8 @@ def compose(self) -> ComposeResult:
             id="messagebox_top_container",
         )
 
+        yield self.top_container
+
     def on_mount(self) -> None:
         """Update widgets immediately after mounting."""
         if self.border_color == "red":
@@ -93,6 +109,9 @@ def on_mount(self) -> None:
             color,
         )
 
+        self.top_container.styles.width = self.top_container_width
+        self.top_container.styles.height = self.top_container_height
+
     def on_button_pressed(self) -> None:
         """Handle button press."""
         self.dismiss(True)
@@ -218,24 +237,70 @@ def on_button_pressed(self, event: Button.Pressed) -> None:
             self.dismiss()
 
     async def handle_transfer_and_update_ui_when_complete(self) -> None:
-        """Run the data transfer worker and updates the UI on completion."""
-        data_transfer_worker = self.transfer_func()
-        await data_transfer_worker.wait()
-        success, output = data_transfer_worker.result
-        self.dismiss()
-
-        if success:
-            self.app.push_screen(
-                MessageBox(
-                    "Transfer finished."
-                    "\n\n"
-                    "Check the most recent logs to "
-                    "ensure transfer completed successfully.",
-                    border_color="grey",
+        """Run the data transfer worker and updates the UI on completion.
+
+        Note this function is very similar to `log_rclone_copy_errors_api`
+        but kept separate for flexibility.
+        """
+        try:
+            data_transfer_worker = self.transfer_func()
+            await data_transfer_worker.wait()
+            success, output = data_transfer_worker.result
+
+            self.dismiss()
+
+            if success:
+                errors = output
+
+                errors_message = ""
+
+                messagebox_kwargs = {}
+
+                no_transfer_col = (
+                    "blue"
+                    if self.app.theme == "textual-light"
+                    else "lightblue"
                 )
-            )
-        else:
-            self.app.show_modal_error_dialog(output)
+
+                if errors["nothing_was_transferred_rawdata"] is True:
+                    errors_message += f"[{no_transfer_col}]\nNothing was transferred from rawdata.[/{no_transfer_col}]\n"
+
+                if errors["nothing_was_transferred_derivatives"] is True:
+                    errors_message += f"[{no_transfer_col}]\nNothing was transferred from derivatives.[/{no_transfer_col}]\n"
+
+                if any(errors["messages"]):
+                    if errors["file_names"]:
+                        errors_message += (
+                            "\n[red]Errors detected! in files:[/red]\n"
+                        )
+                        errors_message += "\n".join(errors["file_names"])
+                    else:
+                        errors_message += "\n[red]Errors detected![/red]"
+                    errors_message += (
+                        "[red]\n\nThe error messages are:[/red]\n"
+                    )
+                    errors_message += "\n\n".join(errors["messages"])
+                    messagebox_kwargs = {"width": "75%", "height": "75%"}
+
+                if errors_message == "":
+                    errors_message += "No errors detected"
+
+                message = (
+                    f"Transfer finished.\n"
+                    f"{errors_message}\n\n"
+                    f"Check the most recent logs for full details."
+                )
+
+                self.app.push_screen(
+                    MessageBox(
+                        message, border_color="grey", **messagebox_kwargs
+                    )
+                )
+            else:
+                self.app.show_modal_error_dialog(output)
+
+        except BaseException as e:
+            self.app.show_modal_error_dialog(str(e))
 
 
 class SearchingCentralForNextSubSesPopup(ModalScreen):
diff --git a/datashuttle/utils/custom_types.py b/datashuttle/utils/custom_types.py
index 44c8de353..af5c48124 100644
--- a/datashuttle/utils/custom_types.py
+++ b/datashuttle/utils/custom_types.py
@@ -1,4 +1,6 @@
-from typing import Any, Literal, Tuple
+from __future__ import annotations
+
+from typing import Any, Literal, Tuple, TypedDict
 
 DisplayMode = Literal["error", "warn", "print"]
 
@@ -13,3 +15,12 @@
 ConnectionMethods = Literal[
     "ssh", "local_filesystem", "gdrive", "aws", "local_only"
 ]
+
+
+class TransferErrors(TypedDict):
+    """Type `errors` dictionary (used for collecting `rclone copy` output)."""
+
+    file_names: list[str]
+    messages: list[str]
+    nothing_was_transferred_rawdata: bool | None
+    nothing_was_transferred_derivatives: bool | None
diff --git a/datashuttle/utils/data_transfer.py b/datashuttle/utils/data_transfer.py
index c21d39bda..c7a021d47 100644
--- a/datashuttle/utils/data_transfer.py
+++ b/datashuttle/utils/data_transfer.py
@@ -33,7 +33,6 @@ def __init__(
         datatype: Union[str, List[str]],
         overwrite_existing_files: OverwriteExistingFiles,
         dry_run: bool,
-        log: bool,
     ):
         """Initialise TransferData.
 
@@ -71,9 +70,6 @@ def __init__(
             Perform a dry-run of transfer. This will output as if file
             transfer was taking place, but no files will be moved.
 
-        log
-            if `True`, log and print the transfer output.
-
         """
         self.__cfg = cfg
         self.__upload_or_download = upload_or_download
@@ -84,6 +80,8 @@ def __init__(
         self.__base_folder = self.__cfg.get_base_folder(
             self.__local_or_central, self.__top_level_folder
         )
+        self.__overwrite_existing_files = overwrite_existing_files
+        self.__dry_run = dry_run
 
         self.sub_names = self.to_list(sub_names)
         self.ses_names = self.to_list(ses_names)
@@ -91,6 +89,8 @@ def __init__(
 
         self.check_input_arguments()
 
+    def run(self):
+        """Run the transfer."""
         include_list = self.build_a_list_of_all_files_and_folders_to_transfer()
 
         if any(include_list):
@@ -99,16 +99,29 @@ def __init__(
                 self.__upload_or_download,
                 self.__top_level_folder,
                 include_list,
-                cfg.make_rclone_transfer_options(
-                    overwrite_existing_files, dry_run
+                self.__cfg.make_rclone_transfer_options(
+                    self.__overwrite_existing_files, self.__dry_run
                 ),
             )
 
-            if log:
-                utils.log_and_message(output.stderr.decode("utf-8"))
+            stdout, stderr, errors = rclone.parse_rclone_copy_output(
+                self.__top_level_folder, output
+            )
+
+            if output.returncode != 0 and not any(errors["messages"]):
+                raise RuntimeError(
+                    "Errors were detected in transfer but not reported properly. "
+                    "Please contact the datashuttle team."
+                )
+
+            rclone.log_stdout_stderr_python_api(stdout, stderr)
+
         else:
-            if log:
-                utils.log_and_message("No files included. None transferred.")
+            utils.log_and_message("No files included. None transferred.")
+            errors = rclone.get_empty_errors_dict()
+            errors[f"nothing_was_transferred_{self.__top_level_folder}"] = True
+
+        return errors
 
     # -------------------------------------------------------------------------
     # Build the --include list
diff --git a/datashuttle/utils/rclone.py b/datashuttle/utils/rclone.py
index fe1909119..e87deb779 100644
--- a/datashuttle/utils/rclone.py
+++ b/datashuttle/utils/rclone.py
@@ -4,13 +4,15 @@
 
 if TYPE_CHECKING:
     from datashuttle.configs.config_class import Configs
-    from datashuttle.utils.custom_types import TopLevelFolder
+    from datashuttle.utils.custom_types import TopLevelFolder, TransferErrors
 
+import json
 import os
 import platform
 import shlex
 import subprocess
 import tempfile
+from pathlib import Path
 from subprocess import CompletedProcess
 
 from datashuttle.configs import canonical_configs
@@ -461,19 +463,206 @@ def transfer_data(
         output = call_rclone_through_script(
             f"{rclone_args('copy')} "
             f'"{local_filepath}" "{cfg.get_rclone_config_name()}:'
-            f'{central_filepath}" {extra_arguments}',
+            f'{central_filepath}" {extra_arguments} --use-json-log',
         )
 
     elif upload_or_download == "download":
         output = call_rclone_through_script(
             f"{rclone_args('copy')} "
             f'"{cfg.get_rclone_config_name()}:'
-            f'{central_filepath}" "{local_filepath}"  {extra_arguments}',
+            f'{central_filepath}" "{local_filepath}" {extra_arguments} --use-json-log',
         )
 
     return output
 
 
+def log_stdout_stderr_python_api(stdout: str, stderr: str) -> None:
+    """Log `stdout` and `stderr`."""
+    message = (
+        f"\n\n**************  STDOUT  **************\n"
+        f"{stdout}"
+        f"\n\n**************  STDERR  **************\n"
+        f"{stderr}"
+    )
+
+    utils.log_and_message(message)
+
+
+def log_rclone_copy_errors_api(errors):
+    """Log the `errors` dictionary.
+
+    The `errors` dictionary contains all pertinent information on
+    issues that occurred when running `rclone copy`. Note this logs
+    for the API, the TUI display is handled separately.
+
+    Note this function is very similar
+    to `handle_transfer_and_update_ui_when_complete`
+    but kept separate for flexibility.
+    """
+    message = ""
+
+    if errors["nothing_was_transferred_rawdata"] is True:
+        message += "\n\nNothing was transferred from rawdata.\n"
+
+    if errors["nothing_was_transferred_derivatives"] is True:
+        message += "\n\nNothing was transferred from derivatives.\n"
+
+    if any(errors["messages"]):
+        if any(errors["file_names"]):
+            message += (
+                "\n\nErrors were detected! In files:"
+                "\n-------------------------------\n"
+            )
+            message += "\n".join(errors["file_names"])
+        else:
+            message += "\n\n[red]Errors detected![/red]"
+        message += "\n\nThe error messages are:\n-----------------------\n"
+        message += "\n".join(errors["messages"])
+        message += "\n"
+
+    if message == "":
+        message = "No errors detected"
+
+    utils.log_and_message(message, use_rich=True)
+
+
+def parse_rclone_copy_output(top_level_folder, output):
+    """Format the `rclone copy` output ready for logging.
+
+    Reformat and combine the string streams and `errors`
+    dictionary from stdout and stderr output of `rclone copy`.
+    see `reformat_rclone_copy_output() for details.
+    """
+    stdout, out_errors = reformat_rclone_copy_output(
+        output.stdout, top_level_folder=top_level_folder
+    )
+
+    stderr, err_errors = reformat_rclone_copy_output(
+        output.stderr, top_level_folder=top_level_folder
+    )
+
+    # Combine the two `errors` output
+    all_errors = {
+        "file_names": out_errors["file_names"] + err_errors["file_names"],
+        "messages": out_errors["messages"] + err_errors["messages"],
+        "nothing_was_transferred_rawdata": err_errors[
+            "nothing_was_transferred_rawdata"
+        ],
+        "nothing_was_transferred_derivatives": err_errors[
+            "nothing_was_transferred_derivatives"
+        ],
+    }
+
+    all_errors["file_names"] = list(set(all_errors["file_names"]))
+
+    return stdout, stderr, all_errors
+
+
+def get_empty_errors_dict() -> TransferErrors:
+    """Return the `errors` dictionary with default values.
+
+    The `errors` dictionary holds information
+    about errors which occurred during `rclone copy` transfer.
+    The dict entries are:
+
+    file_names
+        A list of file names associated with errors.
+
+    messages
+        A list of messages associated with errors. For each file name,
+        there will be an associated message, but it is also possible to
+        have messages that are not associated with any file name.
+
+    nothing_was_transferred_rawdata
+        A flag that can take the value `None`, `True` or `False`.
+        If `None`, this top-level folder was not attempted to be transferred.
+        If `True`, it was attempted and nothing was transferred. If `False`,
+        it was attempted and something was transferred.
+
+    nothing_was_transferred_derivatives
+        See `nothing_was_transferred_rawdata`, this is the equivalent for
+        the derivatives' folder.
+
+    The rawdata and derivatives flags must be split as some functions
+    transfer a single, or both, top level folders in one command.
+    """
+    return {
+        "file_names": [],
+        "messages": [],
+        "nothing_was_transferred_rawdata": None,
+        "nothing_was_transferred_derivatives": None,
+    }
+
+
+def reformat_rclone_copy_output(
+    stream: bytes,
+    top_level_folder: TopLevelFolder | None = None,
+) -> tuple[str, TransferErrors]:
+    """Parse the output of `rclone copy` for convenient error checking.
+
+    Rclone's `copy` command (called with `--use-json-log`) outputs a lot of
+    information related to the transfer. We dump this in text form to a log
+    file. However, we also want to grab any key events (errors, or complete
+    lack of transferred files) so these can be displayed separately.
+
+    This function iterates through all lines in the `rclone copy` output.
+    This output is typically a mix of string format and json format.
+    If the line is json-encoded, then we extract important information
+    and format it to string, and re-insert it into the output.
+
+    In this way, we have a string-format output ready to be
+    dumped to the logs, as well as an `errors` dictionary containing
+    details on all key information.
+
+    Returns
+    -------
+    format_stream
+        The input stream, converted to string and with all
+        json-formatted lines reformatted as string. This is ready
+        to be dumped to a log file.
+
+    errors
+        A dictionary (`TransferErrors`) containing key information
+        about issues in the transfer.
+
+    """
+    split_stream = stream.decode("utf-8").split("\n")
+
+    errors = get_empty_errors_dict()
+
+    for idx, line in enumerate(split_stream):
+        try:
+            line_json = json.loads(line)
+        except json.JSONDecodeError:
+            continue
+
+        if line_json["level"] in ["error", "critical"]:
+            if "object" in line_json:
+                full_filepath = Path(
+                    f"{top_level_folder}/{line_json['object']}"
+                ).as_posix()
+                errors["file_names"].append(full_filepath)
+                errors["messages"].append(
+                    f"The file {full_filepath} failed to transfer. Reason: {line_json['msg']}"
+                )
+            else:
+                errors["messages"].append(f"ERROR : {line_json['msg']}")
+
+        elif "stats" in line_json and "totalTransfers" in line_json["stats"]:
+            if line_json["stats"]["totalTransfers"] == 0:
+                errors[f"nothing_was_transferred_{top_level_folder}"] = True  # type:ignore
+            else:
+                errors[f"nothing_was_transferred_{top_level_folder}"] = False  # type:ignore
+
+        split_stream[idx] = (
+            f"{line_json['time'][:19]} {line_json['level'].upper()} : {line_json['msg']}"
+        )
+
+    format_stream = "\n".join(split_stream)
+
+    return format_stream, errors
+
+
 def get_local_and_central_file_differences(
     cfg: Configs,
     top_level_folders_to_check: List[TopLevelFolder],
diff --git a/datashuttle/utils/ssh.py b/datashuttle/utils/ssh.py
index c7d6256a4..b31379c1c 100644
--- a/datashuttle/utils/ssh.py
+++ b/datashuttle/utils/ssh.py
@@ -210,7 +210,7 @@ def connect_client(
             f"3) The central_host_id: {cfg['central_host_id']} is"
             f" correct.\n"
             f"4) The central username:"
-            f" {cfg['central_host_username']}, and password are correct."
+            f" {cfg['central_host_username']}, and password are correct.\n"
             f"Original error: {e}",
             ConnectionError,
         )
diff --git a/pyproject.toml b/pyproject.toml
index 2e9402411..66abee6c1 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -67,6 +67,7 @@ dev = [
     "types-setuptools",
     "pytest-asyncio",
     "validators",
+    "filelock"
 ]
 
 [build-system]
diff --git a/tests/test_utils.py b/tests/test_utils.py
index bb38c5851..54f80a21b 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -6,6 +6,8 @@
 import os
 import pathlib
 import shutil
+import threading
+import time
 import warnings
 from os.path import join
 from pathlib import Path
@@ -728,3 +730,21 @@ def mock_get_datashuttle_path():
         "datashuttle.configs.canonical_folders.get_datashuttle_path",
         mock_get_datashuttle_path,
     )
+
+
+def lock_a_file(file_path, duration=5):
+    """"""
+
+    def continually_write_to_file(path, duration):
+        end_time = time.time() + duration
+        with open(path, "a") as f:
+            while time.time() < end_time:
+                f.write("LOCKED\n")
+                f.flush()
+
+    t = threading.Thread(
+        target=continually_write_to_file, args=(file_path, duration)
+    )
+    t.start()
+
+    return t
diff --git a/tests/tests_integration/test_logging.py b/tests/tests_integration/test_logging.py
index 9b5bd4a0b..233ad3d0b 100644
--- a/tests/tests_integration/test_logging.py
+++ b/tests/tests_integration/test_logging.py
@@ -1,12 +1,15 @@
 import glob
 import logging
 import os
+import platform
 import re
 from pathlib import Path
 
 import pytest
+from filelock import FileLock
 
 from datashuttle.configs import canonical_configs
+from datashuttle.configs.canonical_configs import get_broad_datatypes
 from datashuttle.configs.canonical_tags import tags
 from datashuttle.utils import ds_logger
 from datashuttle.utils.custom_exceptions import (
@@ -482,3 +485,94 @@ def test_validate_names_against_project_logging(self, project):
 
         assert "ERROR" in log
         assert str(e.value) in log
+
+    def test_errors_are_caught_and_logged(self, project):
+        """
+        Create errors in the transfer by locking files, and check
+        the errors are correctly flagged in logs and `errors`. Also,
+        perform a transfer where no files are transferred, and check
+        this is flagged in logs and `errors`.
+        """
+
+        # Set up a folder to transfer
+        subs, sessions = test_utils.get_default_sub_sessions_to_test()
+
+        test_utils.make_and_check_local_project_folders(
+            project,
+            "rawdata",
+            subs,
+            sessions,
+            get_broad_datatypes(),
+        )
+
+        # Lock a file then perform the transfer, causing errors.
+        relative_path = (
+            Path("rawdata")
+            / subs[0]
+            / sessions[0]
+            / "ephys"
+            / "placeholder_file.txt"
+        )
+        a_transferred_file = project.get_local_path() / relative_path
+
+        test_utils.delete_log_files(project.cfg.logging_path)
+
+        test_utils.delete_log_files(project.cfg.logging_path)
+
+        if platform.system() == "Windows":
+            lock = FileLock(a_transferred_file, timeout=5)
+            with lock:
+                errors = project.upload_custom("rawdata", "all", "all", "all")
+            error_message = "because another process has locked "
+        else:
+            thread = test_utils.lock_a_file(a_transferred_file)
+            errors = project.upload_custom("rawdata", "all", "all", "all")
+            thread.join()
+            error_message = "size changed"
+
+        # Check that errors and logs flag the transfer errors
+        assert errors["file_names"] == [relative_path.as_posix()]
+        assert error_message in errors["messages"][0]
+
+        log = test_utils.read_log_file(project.cfg.logging_path)
+
+        assert Path(errors["file_names"][0]).as_posix() in log
+        assert "Errors were detected!" in log
+        assert error_message in log
+
+        # now just upload everything
+        project.upload_entire_project()
+        test_utils.delete_log_files(project.cfg.logging_path)
+
+        # Check that it is flagged that no transfer took place for rawdata
+        errors = project.upload_custom("rawdata", "all", "all", "all")
+
+        assert errors["nothing_was_transferred_rawdata"] is True
+        assert errors["nothing_was_transferred_derivatives"] is None
+
+        log = test_utils.read_log_file(project.cfg.logging_path)
+        assert "Nothing was transferred from rawdata." in log
+
+        test_utils.delete_log_files(project.cfg.logging_path)
+
+        # Check that it is flagged that no transfer took place for derivatives
+        errors = project.upload_custom("derivatives", "all", "all", "all")
+
+        assert errors["nothing_was_transferred_rawdata"] is None
+        assert errors["nothing_was_transferred_derivatives"] is True
+
+        log = test_utils.read_log_file(project.cfg.logging_path)
+        assert "Nothing was transferred from derivatives." in log
+
+        test_utils.delete_log_files(project.cfg.logging_path)
+
+        # Check that it is flagged that no transfer took place
+        # for both rawdata and derivatives
+        errors = project.upload_entire_project()
+
+        assert errors["nothing_was_transferred_rawdata"] is True
+        assert errors["nothing_was_transferred_derivatives"] is True
+
+        log = test_utils.read_log_file(project.cfg.logging_path)
+        assert "Nothing was transferred from rawdata." in log
+        assert "Nothing was transferred from derivatives." in log
diff --git a/tests/tests_transfers/local_filesystem/test_transfer.py b/tests/tests_transfers/local_filesystem/test_transfer.py
index b924650e5..039300a55 100644
--- a/tests/tests_transfers/local_filesystem/test_transfer.py
+++ b/tests/tests_transfers/local_filesystem/test_transfer.py
@@ -641,6 +641,90 @@ def test_overwrite_different_size_different_times(
         elif overwrite_existing_files == "always":
             assert test_utils.read_file(central_file_path) == ["file earlier"]
 
+    def test_errors_variable(self, project, monkeypatch):
+        """
+        Test that the `errors` variable is correctly
+        returned from every transfer function. `errors` is a variable
+        that contains information about any errors that were encountered
+        during transfer.
+        """
+
+        # Monkeypatch the error-parsing function so it returns
+        # predictable values.
+        import datashuttle
+
+        def test_errors(top_level_folder):
+            return {
+                "file_names": [f"{top_level_folder}/hello_world.txt"],
+                "messages": ["how are you?"],
+                "nothing_was_transferred_rawdata": None,
+                "nothing_was_transferred_derivatives": None,
+            }
+
+        def monkeypatch_parse_output(top_level_folder, b):
+            stdout = "stdout"
+            stderr = "stderr"
+            return stdout, stderr, test_errors(top_level_folder)
+
+        monkeypatch.setattr(
+            datashuttle.utils.rclone,
+            "parse_rclone_copy_output",
+            monkeypatch_parse_output,
+        )
+
+        # Generate some test files so the transfer runs properly
+        subs, sessions = test_utils.get_default_sub_sessions_to_test()
+
+        for top_level_folder in ["rawdata", "derivatives"]:
+            test_utils.make_and_check_local_project_folders(
+                project,
+                top_level_folder,
+                subs,
+                sessions,
+                get_broad_datatypes(),
+            )
+
+        # Run every transfer function and check that
+        # `errors` is returned correctly.
+        specific_file = (
+            lambda path_: f"{path_}/rawdata/{subs[0]}/{sessions[0]}/ephys/placeholder_file.txt"
+        )
+
+        # All 'rawdata' functions
+        for func in [
+            lambda: project.upload_specific_folder_or_file(
+                specific_file(project.get_local_path())
+            ),
+            lambda: project.download_specific_folder_or_file(
+                specific_file(project.get_central_path())
+            ),
+            lambda: project.upload_custom("rawdata", "all", "all", "all"),
+            lambda: project.download_custom("rawdata", "all", "all", "all"),
+            project.upload_rawdata,
+            project.download_rawdata,
+        ]:
+            assert func() == test_errors("rawdata")
+
+        # All 'derivatives' functions
+        for func in [project.upload_derivatives, project.download_derivatives]:
+            assert func() == test_errors("derivatives")
+
+        # Entire project functions should merge the errors
+        # of rawdata and derivatives
+        for func in [
+            project.upload_entire_project,
+            project.download_entire_project,
+        ]:
+            assert func() == {
+                "file_names": [
+                    "rawdata/hello_world.txt",
+                    "derivatives/hello_world.txt",
+                ],
+                "messages": ["how are you?", "how are you?"],
+                "nothing_was_transferred_rawdata": None,
+                "nothing_was_transferred_derivatives": None,
+            }
+
     def get_paths_to_a_local_and_central_file(self, project, top_level_folder):
         path_to_test_file = (
             Path(top_level_folder)
diff --git a/tests/tests_tui/test_tui_transfer.py b/tests/tests_tui/test_tui_transfer.py
index 03b036508..67a46606a 100644
--- a/tests/tests_tui/test_tui_transfer.py
+++ b/tests/tests_tui/test_tui_transfer.py
@@ -1,4 +1,8 @@
+import platform
+from pathlib import Path
+
 import pytest
+from filelock import FileLock
 
 from datashuttle.configs import canonical_configs
 from datashuttle.tui.app import TuiApp
@@ -218,6 +222,86 @@ async def test_transfer_custom(
 
             await pilot.pause()
 
+    @pytest.mark.asyncio
+    async def test_errors_are_reported_on_pop_up(self, setup_project_paths):
+        """
+        Check that transfer errors, or the case where no files are transferred,
+        are displayed properly on the modal dialog that displays following
+        the transfer.
+        """
+        tmp_config_path, tmp_path, project_name = setup_project_paths.values()
+
+        subs, sessions = test_utils.get_default_sub_sessions_to_test()
+
+        app = TuiApp()
+        async with app.run_test(size=self.tui_size()) as pilot:
+            # Set up the project files to transfer and navigate
+            # to the transfer screen
+            await self.check_and_click_onto_existing_project(
+                pilot, project_name
+            )
+            await self.switch_tab(pilot, "transfer")
+
+            project = pilot.app.screen.interface.project
+
+            self.setup_project_for_data_transfer(
+                project,
+                subs,
+                sessions,
+                ["rawdata", "derivatives"],
+                "upload",
+            )
+
+            relative_path = (
+                Path("rawdata")
+                / subs[0]
+                / sessions[0]
+                / "ephys"
+                / "placeholder_file.txt"
+            )
+
+            # Lock a file and perform the transfer, which will have errors.
+            # Check the errors are displayed in the pop-up window.
+            a_transferred_file = project.get_local_path() / relative_path
+
+            if platform.system() == "Windows":
+                lock = FileLock(a_transferred_file, timeout=5)
+                with lock:
+                    await self.run_transfer(
+                        pilot, "upload", close_final_messagebox=False
+                    )
+                error_message = "because another process has locked "
+            else:
+                thread = test_utils.lock_a_file(
+                    a_transferred_file, duration=20
+                )
+
+                await self.run_transfer(
+                    pilot, "upload", close_final_messagebox=False
+                )
+                thread.join()
+                error_message = "size changed"
+
+            displayed_message = app.screen.message
+
+            assert relative_path.as_posix() in displayed_message
+
+            assert error_message in displayed_message
+
+            await self.close_messagebox(pilot)
+
+            # Transfer again to check the message displays indicating
+            # no files were transferred.
+            await self.run_transfer(pilot, "upload")
+
+            await self.run_transfer(
+                pilot, "upload", close_final_messagebox=False
+            )
+
+            assert "Nothing was transferred from rawdata" in app.screen.message
+
+            await pilot.pause()
+
     async def switch_top_level_folder_select(
         self, pilot, id, top_level_folder
     ):
@@ -227,14 +311,16 @@ async def switch_top_level_folder_select(
             await self.move_select_to_position(pilot, id, position=5)
             assert pilot.app.screen.query_one(id).value == "derivatives"
 
-    async def run_transfer(self, pilot, upload_or_download):
+    async def run_transfer(
+        self, pilot, upload_or_download, close_final_messagebox=True
+    ):
         # Check assumed default is correct on the transfer switch
         assert pilot.app.screen.query_one("#transfer_switch").value is False
 
         if upload_or_download == "download":
             await self.scroll_to_click_pause(pilot, "#transfer_switch")
 
-        await self.click_and_await_transfer(pilot)
+        await self.click_and_await_transfer(pilot, close_final_messagebox)
 
     def setup_project_for_data_transfer(
         self,
diff --git a/tests/tests_tui/tui_base.py b/tests/tests_tui/tui_base.py
index a0c8f16d6..2d08e5ffe 100644
--- a/tests/tests_tui/tui_base.py
+++ b/tests/tests_tui/tui_base.py
@@ -239,7 +239,9 @@ async def move_select_to_position(self, pilot, id, position):
         await pilot.click(id, offset=(2, position))
         await pilot.pause()
 
-    async def click_and_await_transfer(self, pilot):
+    async def click_and_await_transfer(
+        self, pilot, close_final_messagebox=True
+    ):
         await self.scroll_to_click_pause(pilot, "#transfer_transfer_button")
         await self.scroll_to_click_pause(pilot, "#confirm_ok_button")
 
@@ -248,7 +250,8 @@ async def click_and_await_transfer(self, pilot):
         if transfer_task:
             await transfer_task
 
-        await self.close_messagebox(pilot)
+        if close_final_messagebox:
+            await self.close_messagebox(pilot)
 
     async def double_click_input(self, pilot, sub_or_ses, control=False):
         """Helper function to double click input to suggest next sub or ses.