Below are the settings for the monitors, the MacBook and the External Display (DELL)
I changed the prefs to have both CLOSED at STARTUP and to use the SIDEBAR.
Now I cannot reproduce the problem… which is both a good and a bad thing I guess.
Next time this happens I will refer to your instructions and try changing the prefs (if I can access them).
I think the solution is going to be something in that PREFS screen, the only issue is that when the problem occurs I cannot access that PREFS screen as it only shows when the Inspector/INFO panel is open.
Is there a way to add a keyboard shortcut to access the PREFS screen (or maybe CTRL/CLICK on the INFO button) that would open that PREFS as a WINDOW so that it could be changed if needed ?