I'm getting sporadic occasions where undo just doesn't work - e.g. I'll insert a new figure, press Cmd+Z, and nothing happens, no matter how many times I undo - the action cannot be undone. same for rearranging sections, as I've mentioned previously. Unfortunately(?), this does not fail consistently, otherwise I would send you a screencast, but nevertheless I would suggest taking a look at your Undo-related code, because there seems to be a problem there.

Cheers,
Oliver.