Hello, is this on every scene or is it possibly only at the border gate?
I have a theory that you may have given me insight how to improve performance, which is because of the Godrays in the scene.
Most of the background switching day can trigger 10-30sec of 100% cpu hogging whil I have a black screen, for me.
Some few times, some scenes load faster, no clue why.
Have you tried updating your drivers? This sounds like it could be WebGL issue.