Undo Does Not Work


I have an issue with an UNDo function. Very often it does nothing. SU persists adding ALT+BACKSPACE as an UNDo shortcut. I have added as well CRTL+Z one.

Evidently there is some problems with the SU and it is very annoying.
Please advice.

Thank you in advance

What version of SketchUp are you using. Please complete your profile.