The join function doesn't seem to be working very well. I tried sticking the two parts of North Sea Hijack together, it seems to have done it but showed no progress in the bar until I refreshed the page, didn't go back to the media list when clicked, and named the file "North.ts" when I asked for "North Sea Hijack".
Update: tried another and it behaved as expected (not sure about the naming, it was one word). Took an age to clock up to 100%, when it arrived there was a completion report. Tried the North Sea Hijack again, and the same thing happened as before. No progress until (after a while) I refreshed the screen, at which it was 100% with no progress report, and a resulting file called "North" the right size. Checked it over and it plays fine, seems to be complete.
In another situation I tried to cut&paste a .mp4 into a folder, and it refused to move.