One thing I notice is that when I first launch the engine the effect is not visible in the viewport. It only becomes apparent after I play the game in the pop-out window.
I also use emissive lighting for all the ceiling lights.
Emissive Material Settings:
I seen that you commented on another thread that I am looking at to try and get some help with this issue.
Here are my post process volume lumen settings:
Lumen On:
Lumen Off:
My walls and ceilings are single faced planes. I thought maybe that could be the issue since they were too thin but the issue happens outside of the walled interior too.
Lumen Project Settings:
