I have found the following failure in the "Full Screen" function (build 6.7.2.4139 64bit, Windows 10):
Monitor 1: 3840x2160 (4K)
Monitor 2: 2560x1600 (WQGA)
Start Photo Supremen on Monitor 1 (4K) --> Full Screen --> ok
Start Photo Supremen on Monitor 2 (WQGA) --> Full Screen --> The Picture diplayed on Screen area top left with reduced size
I think that's a failure, don't you?