Ok When I don't use shader's i have one...This is just in certain rooms..




Here is the settings..

Yep the bug is well known, has been reported here for a few times.

That only happens if you use shaders, the reason is pretty much unknown, but the fix in on the way.

Till then I suggest that you use non-shaders or use shaders like this.

Note that this only happens in a few cases.