
I did reinstall drivers, but that seemed to have no effect. This also is only an issue with extended desktop, no issue with mirroring. Total guess: something is up with the primary display and hiDPI adjustment in Win10.

The external display is set to full resolution (2560x1440) with no “zoom” (as it had been). I now have the Macbook set to a resolution of 1920x1200 (it’s a 2012 retina, so a bit more than half resolution), set the laptop display to be the primary display, with a “Change the size of text, apps, and other items” to 100% (previously I had it zoomed in a bit on the MBP display). The issue seemed to be fixed once I messed about with the Display Settings. NVidia driver 355.62 + PhysX (no GeForce Experience, HD Audio Driver or 3D Vision, though those files were not installed when I found I had the problem yet again) Windows 10 (with Windows malware tool turned off) I don’t think it’s tied to the driver itself at this point.

I seem to have fixed it once more, but I don’t know how. Just as confused as before – after booting back up after 24hrs I had the same issue all over again.
