Hi Krxtopher, thanks for your reply.
I set the Static Lighting Level Scale to 0.15 just to see if it would fix the issue. (As I saw many Archvis Lighting setups have such a low number) Usually I always leave it to 1. I noticed however that setting the “Static Lighting Level Scale” to 0.15 increased the fequency of the orange spots on the meshes.
Turning “Compress Lightmaps” off, increased the amount of artifacts, and their size. The orange now covers the entire mesh.
The only real solution so far, is to set the “Indirect Lighting Quality” to 10+, but thats not really a long term solution.