Transmission

I have Transmission set to run a bash script each time a torrent finishes - the script simply moves any media files in the torrent into my media folder. When I run the script manually it works perfectly, but when it runs via Transmission the media file is renamed to something like "GMFKRP~C" with no extension - if I rename that file to movie.mp4 it's fine, so the file isn't corrupt, it's just being given a strange filename.

I'd appreciate any help in debugging this - it's difficult to reproduce because any time I run the script myself it works perfectly. Are there any logs I can check etc? Thanks.