Hi All, this is issue is regarding moving virtual monitors to a specific host monitor. There are 3 host and 2 vm monitors but the virtual monitors refuse to move to 1 (main) specific host monitor in Full Screen mode. it is fine in scaled mode.
I suspect because it needs enough graphics memory to run the host screen. My only suggestion would be to install a second graphics card. I would also see if the same issue happens in virthmanager, much better all round than virtual-box.