Failed to Copy Files when installing FTB modpacks

[cassandra-n-w]

Operating System

Linux

Version of PolyMC

PolyMC 7.0. Specifically, the current flatpak version with build date 2025-02-15

Version of Qt

Qt 5.15.10

Description of bug

I attempted to install an FTB modpack. I expected the modpack would be installed. However, after the downloading progress bar finishes, the installation fails with error "Failed to Copy Files", and the instance is not installed.

Note: Installing vanilla minecraft works fine. Installing CurseForge modpacks (e.g. StoneBlock 3) also works fine. The issue seems limited to FTB modpacks, from my limited testing.

Here is the tail of the log file:

1636.698 D Download succeeded: "https://mediafilez.forgecdn.net/files/5897/690/titanium-1.21-4.0.30.jar" 1636.726 D Download succeeded: "https://mediafilez.forgecdn.net/files/5891/67/trashcans-1.0.18c-neoforge-mc1.21.jar" 1636.727 D Task "Net::Download(0x5559ca4f2cd0)" restarting for after failing at first 1636.727 D Downloading "https://mediafilez.forgecdn.net/files/775/554/v.3.0_The_Academy.zip" 1636.969 W Checksum mismatch, download is bad. 1636.969 D Download failed to finalize: "https://mediafilez.forgecdn.net/files/775/554/v.3.0_The_Academy.zip" 1636.969 D Task "Net::Download(0x5559ca4f2cd0)" restarting for after failing at first 1636.970 D Downloading "https://mediafilez.forgecdn.net/files/775/554/v.3.0_The_Academy.zip" 1637.110 W Checksum mismatch, download is bad. 1637.110 D Download failed to finalize: "https://mediafilez.forgecdn.net/files/775/554/v.3.0_The_Academy.zip" 1637.110 D Task "NetJob(Mod download)" succeeded 1637.629 W Failed to copy files: "No such file or directory" 1637.629 D Source file: "/home/cassie/.var/app/org.polymc.PolyMC/data/PolyMC/cache/ModpacksCHPacks/mekanism_unleashed-1.21-0.2.1-b8f78575d107c43ff616b044b1403f9661d9ef75.jar" 1637.629 D Destination file: "/home/cassie/.var/app/org.polymc.PolyMC/data/PolyMC/instances/.LAUNCHER_TEMP/{c9b9fb70-194f-49af-b630-fd3f07c98072}/minecraft/mods/mekanism_unleashed-1.21-0.2.1.jar" 1637.629 W Failed to copy "/home/cassie/.var/app/org.polymc.PolyMC/data/PolyMC/cache/ModpacksCHPacks/mekanism_unleashed-1.21-0.2.1-b8f78575d107c43ff616b044b1403f9661d9ef75.jar" to "/home/cassie/.var/app/org.polymc.PolyMC/data/PolyMC/instances/.LAUNCHER_TEMP/{c9b9fb70-194f-49af-b630-fd3f07c98072}/minecraft/mods/mekanism_unleashed-1.21-0.2.1.jar" 1637.629 C Task "ModpacksCH::PackInstallTask(0x5559cb393220)" failed: "Failed to copy files" 1637.782 C Task "InstanceStaging(0x5559caf543f0)" failed: "Failed to copy files" 1637.784 D MainWindow::runModalTask: execWithTask exited properly 1666.969 D [HttpMetaCache] Saving metacache with 20 entries

Full log here:
PolyMC-0.log

Steps to reproduce

I am running this on Linux Mint.

Open PolyMC (brand new flatpak installation, haven't configured anything)
Click "Add Instance" button
Click "FTB" tab
Select "FTB Evolution", with version 1.3.0 (also tried with Direwolf20 1.21)
Click "OK" to install

The installer downloads the files, then fails with the error message "Failed to Copy Files".

Suspected cause

No response

This issue is unique

• I have searched the issue tracker and did not find an issue describing my bug.

[cassandra-n-w]

Additional information: Installing FTB Evolution using the CurseForge tab, rather than the FTB tab, works fine. This seems to be a straightforward workaround.

[0verEngineer]

I have the same problem on windows