The undo is broken in the beta. I don’t think it’s a tool specific issue, but it’s always reproducable with contiguous selection tool :
1 load any image
2 Select an area with contiguous selection tool > erase
3 Repeat step 2 multiple times, and try to get back where you started using undo function
The result : Some areas is gonna remain empty and not get restored, as if that part of the data is permanently gone.
I think it’s this issue that hasn’t fixed yet. -> https://bugs.kde.org/show_bug.cgi?id=419891
************************Sorry that I made 1 mistake, this contiguous selection bug also happens in 4.2.9 too and if that’s the case it seems to be a different issue than the bug in this link. Anyway in both cases, undo is broken in the beta.