Something happened to my project, when I try to play it in VR mode. I see this. Only Green top left part is rendered correctly. Other part - blue one - became strange, looks like it is not cleared and not redraw at all, or is redraw very rarely.
There is currently a known issue, UE-16673, where the screen flickers and becomes overly bright when adding a widget to the screen. Does this sound like what you are experiencing? If so, I will increase the community interest on this bug.