Dual Monitor - extended screen mode problem (under Windows 10, 1903)

Release 3.2.4 has made substantial improvements here. In particular the window was making a call to this broken microsoft function even when it wasn’t needed (when you haven’t actually gamma-corrected your monitor). So if you aren’t a vision scientist needing linearised monitors then that version should now give you no issues.

If you do need gamma correction as well as extended desktop then I’m afraid you’ll just have to wait for MS to fix the underlying bug in their fuction call.