I was having this problem as well with another set of files.
I noticed that if I was downloading, say, only episode 5, then episode 6 would sometimes listed as partially completed as well. Then when I later tried to download episode 6 it would download to 100% but wouldn’t play. Moreover, vlc couldn’t play them as partial files (even removing the .bc! extension and having the file end with .avi). I’m not sure what was going on.
Possible solution:
Right click on the task select the episode you wish to download. Hit ok.
Try doing a manual hash check before downloading an episode. After the manual hash check is complete download the file as usual. Ever since I’ve been doing this I haven’t had any problems, so if my experience is anything to go by, it should work.