I only have this problem with one TV series.
I download the episodes I need as normal via Sonarr. Quality criteria are met, all is good.
But then a few days later huntarr decides to find them and download them again.
Then a few days later.... again... the SAME files downloading, exactly the same release/quality/everything.
I went into sonarr and saw against the series edit the huntarr missing label was there, not sure why ?
I've removed it, and stopped sonarr tracking that series (its complete now), so hopefully that will stop it.
Running 8.2.10