I was able to remove the sploches by turnig off “Affect Dynamic Indirect Lighting” in the mesh.
Max Lumen Mesh Cards did nothing.
However, now I’m having another issue where the spotlight that I added to support the emissive material is very sharp against the wall. Something is weird in 5.8, these issues don’t show up in 5.7.
A simple spotlight comparison:
5.7
5.8
Source radius in the spotlight seems to be doing nothing. And this is on all scalabilities.