I have a MBP (13-inch, 2019) running Catalina 10.15.7. It is connected to an external P27h-20 Display, which I've mirrored to an Artist 15.6 tablet. This has worked just fine in the past. I must have changed something--or things just got restarted--and now when I move the mouse onto the external mirrored display, it appears on both mirrored displays (like it should) but when I move past a certain point, the display on the P27h monitor goes black. If I turn off mirroring, everything works fine. I've tried optimizing the display for both the tablet and the monitor with no change.