If there are duplicate names of files within a NZB set, Altbinz will overwrite one file with the other.
I downloaded a 2-CD set of MP3 files. There were two files both named "playlist.m3u" - one for each CD. Altbinz would only process one M3u file. I originally thought that the 2nd m3u file was missing, so when I downloaded the par2 files to create the other (CD1) m3u file, the existing (CD2) m3u file was overwritten with the other (CD1) m3u file. This kept happening back-and-forth when each new Par2 file was downloaded and processed. (auto-par being enabled)
Quickpar does not have this problem because it renames any duplicate "playlist.m3u" files in the format "playlist[1].m3u, playlist[2].m3u ....
Another small bug:
I don't know if this problem is still current, as it happened about a year or more ago. I downloaded a movie that was one huge single file. (unbelieveable I know!) and it downloaded OK but the filename did not show up at all. (so I had to rename the file "movie.avi") This was not a long filename, which I'm aware has it's own limitations in Windows. I've thankfully never come across any other movies posted as one single huge attachment (surprising that NNTP servers even allow mammoth files) so it's not a critical problem, but I just thought I'd mention it.