Thank you for your response.
Coincidentally, the phone support people sent me here quite some time ago. Their suggestions for fixing the issue were the standard, basic, expected answers. ("Have you downloaded the current video drivers?" Yes. "Have you updated your computer?" Yes.
"Have you uninstalled and reinstalled [insert piece of hardware]?" Yes.) When they got to the "completely reinstall Windows and all of your software" we were done talking.
Oddly, despite my belief and suggestion that this issue started after switching from a 1600x1200 monitor at 100% scaling to a 3840x2160 monitor with 150% scaling, no one has pursued that direction. NOTE: I have two systems (i5 and i7, both Win10, both
mid to high end Nvidia cards) that were both running 1600x1200 at 100% scaling and were changed to 3840x2160 at 150% scaling, and BOTH systems have this issue. This too is an odd coincidence?
:)