I had a very odd thing occur this morning just after opening up a ZTool.
The Smooth brush stopped smoothing and started doing a sort of scrambled inflate on part of my mesh and not working at all on another part of my mesh (NO masking was active) which lead me to believe that my ZTool itself was probably becomming corrupted.
Here is how I fixed it - selected a ZSphere and then appended all of my subtools and then deleted the ZSphere. Not sure if this is something that is widely known, but it worked for me and I have never had it happen since version 2.0 so figured I would share in case it could save someone else a headache.
Oh, I also noticed that my ZTool had started taking over 5 minutes to save just before this occurred and that normally means my tool is becomming corrupted - once I “rebuilt” the tool it saved in under 30 seconds (at lowest level of subdivision in both occassions).