One potential tip for anyone having trouble:
If you happen to be in the fairly rare situation where you're trying to reseed a file from a Windows/Linux machine that was originally downloaded to a Mac and the force recheck doesn't work, the file will need to be reuploaded from a Mac to be reseeded.
Some Mac files still use resource forks... I think MP4s especially. I just had a reseed that was stuck part way through even though the whole file was there after uploading from a Windows machine.
I paused the torrent, deleted the file on my (Linux) seedbox, and reuploaded to the seedbox from a Mac, rechecked again and the recheck completed at 100% and the file is now being reseeded.
Hope this helps someone.