when downloading a torrent with many files the app will get confused. fairly often one file will show as completed until you run the forced recheck, then it will drop down a few tenths of a percentage and continue to download again. if you again use the force recheck the same thing will happen.
sometimes it's much worse where you'll get a massive partfile which almost everything downloaded, or without any rechecking a files percentage will continually cycle between 99.9% and about 97+.
this only happens when you choose a few files out of the torrent because you don't want the rest.