Toolbox installation has rendered Windows VM basically unusable

I recently upgraded my Parallels Desktop for Mac to version 15.1.2; the installation appears to have worked properly. Upon launching the PVM it immediately began installing the Toolbox. This installation failed and left my Windows 7 VM in a terrible state: many preferences were changed, display resolution was set to 800x800, the cursor behaved strangely, the folder linking back to my Mac (OS X 10.14.6) was gone.

This happened on 2 different VM images ... both are now basically unusable.

I have not been able to find anything in the Knowledge Base similar to this.

Any support/guidance would be greatly appreciated.