Actually, there's another reason for sometimes not getting back up to 100% on an individual file. People often include images as well as videos. Those people often include them at the same folder level as the video. People like me don't want / need other peoples' images so delete them.
However, the way files are split in a torrent, the last chunk of a video file may well have been uploaded/downloaded within the image file next to it. Hence, if you no longer have the video file you may also find that the video files above and below it only recheck to 99% or so each.
This may not be an issue if you haven't originally downloaded the image file at all, or it may be. You'll often see part of a file shows as downloaded even if you've unticked it. I'm not sure if that means the full video file has therefore downloaded and be retained.
I get around this by redownloading the images if I get a reseed request, and someone does have the images too, so I become a fully fledged seeder again. Their size is normally minor in comparison to the video files.
