Is the copied file going to a usb? Is the usb fake? Otherwise I’m pretty sure your source is bad. Probably the disk sector if you’re sure the file was at some point complete.
Something like btrfs probably does block cloning or similar so a copy to the same disk probably just points at the same disk blocks as the original.
ffmpeg -v error -i file.avi -f null - 2>error.log
Check the source probably
Who needs 20! Lol. Says more about me than you.