That’s strange. When I first loaded the levelpack, the undo button was completely broken, but when I exited to the menu and loaded the levelpack again, it started working.
Apologies for that; this behavior was due to errors happening after trying to undo when GAME IS X is made, so I disable undoing in this instance.
Problem is, I have no idea why the undo is not restoring itself upon level restart. I will release a fixed version around mid-to-late January to fix it.
Sorry for any inconveniences. 😞