Jean. It happens ONLY when I try undoing a selection
So many questions:
A.) When you Undo are you using
1. Undo Arrow icon up near the printer,
2. Alt Backspace
3. Control Z
4. History (F3) and clicking back one step (clicking the little Undo Redo eye icon)?
B.) Are you working with
1. a single layer
2. one of many layers?
C.) How was the selection made:
1. Selection tool
2. Freehand Selection
3. Magic Wand
4. Smart Selection Brush
5. Auto Selection.
Do any of these alternatives matter or make a difference?
In testing I would load an image - a single layer make a selection with the selection tool , then undo /redo just that a number of times using the undo arrows to see if the problem occurs - ie start with the simplest setting.
Do you have another computer that you can install the current package on to see if the problem persists with different computers or just one - if it occurs with different computers it could be a corrut installation package.
You say that you have uninstalled (and I presume reinstalled around three times). Did you reinstall with the default recommended settings ?
Did you download a fresh installation package.
If it were a common problem then many people would be joining in to this thread with the same problem.
Systems available Win7, Win 8.1,Win 10 Version 1607 Build 14393.2007 & version 20H2 Build 19042.867