ZBrushCentral

zbrush SubTool mesh and history deleted accidentally

I’m new to zbrush and trying to complete some work. I don’t know if this is a bug or something I’m doing wrong, but it’s happened 3 times now in the past 2 days. Any assistance would be greatly appreciated.

Using an Intuos tablet I am clicking/dragging on a subtool mesh surface. I think I hold ctrl + shift or ctrl+ z and click as I’m quickly working.

The result is that all of the geometry of the subtool completely disappears. It’s not visible in the right hand menu. It’s not hidden. AND it seems to delete/purge all history for the subtool as well! Then it has to be reAppended into the menu and all work on it must be restarted.

This third time it happened, Zbrush crashed, froze and had to be closed.

Please let me know if this has happened to anyone else before andif there is a solution.
Thank you!