Screen Flickering in Editor,

So, I’m working on a game right now, and when I was making the walls, ceilings, and lights, I noticed that if I go into the Play Test Mode, and look down, the screen will start to flicker, and instantly stop if I look up again. This has only started happening since I placed the walls, ceilings, and lights, and I am not sure what is causing this.

For the character I took the 3rd Person Model/Template from Unreal, and simply moved the camera into the head of the player.