Hi Art
Sorry I don't know how to solve your problem, but I might have a way for you to "test faster".
When I'm in a situation where an app blocks everything, I do one of 2 things.
The "easy" way.
Sometimes you can just change your desktop then close the app via system-monitor.
Change desktop: Ctrl + Alt + Left/Right Arrow
Close app: Open system-monitor -> kill app
The "hard" way.
If you're unable to switch desktop, you can nearly always close it in another tty layer (this will be in Command-Line-Interface aka CLI)
Switch tty layer: Ctrl + Alt + F key (for example Ctrl + Alt + F4)
Now you're in another tty layer, you should get an login prompt (CLI): login with your user info
Now find the PID ID for the app: use the command "top"
Once you see the ID: use Ctrl + C to close top
Now close the app causing trouble: use this command "sudo kill [Insert PID ID]"
Now logout: command "logout"
Return to your normal tty layer: this should be layer 7 (in my case at least): Ctrl + Alt + F7
Everything should be back to normal.
I hope this helps a tiny bit at least.
Good luck, sorry I couldn't be of more help.