VR Fullscreen off on map change


I have a problem. The Preview Screen - when I am in VR - quits fullscreen mode if I change the map during gameplay.
I try console commend “r.fullscreenmode 0” in the level blueprint of the new loaded level via event begin play but nothing happens. The mode stays in windowed mode.
Can someone tell me how I can stay in fullscreen or how to switch it back on fullscreen if I change the map during gameplay?

I am on 4.18 and have a oculus on windows 10. Everything is up to date.