Hi Roger,
I just noticed a couple more bugs (I think):
1. Undo all sounds sometimes seems to revert only some of the sounds in the beat.
2. If you tweak a sound out (at which point you can of course revert it), then switch to a different beat, then return to the beat in which you tweaked the sound out, you can no longer revert the sound. I guess it's possible that is the desired behaviour? Regardless, it seems logical to me there might be a situation where you tweak out a sound and use it right up to a beat transition, in which case you won't have time to revert it back before you switch beats, creating an issue when you return to the beat in question?