I think it had more to do with the audio than video. From what I think I gathered, Damian's mic got disconnected and no vocals where recorded for the period the mic was off. I also think he mentioned messing up some of the lyrics.
I suggested dubbing (I want a DVD right!) to which Damian smiled disapprovingly and said he's OK to use dubbing for cleaning up but not to replace from scratch.
His Mic did get disconnected at some point, but he grabbed the backup pretty fast and only missed 2-3 words, I believe. I only think it adds to the live feel if they leave it in though. I can also imagine being perfectionist about the dvd and wanting everything going exactly right. They should be able to salvage most of the gig as a sort of bonus on the new album, though?