Lumen GI and Reflections feedback thread

Hey,
anyone knows where these weird lighting splotches are coming from? Backwall.
Preview 2 Lumen in hardware mode on a 3090. LumenGI pretty much maxed out (everything set to 5).
Almost everything Nanite, environment solid.
I changed the lumen settings, changed the amount of lumen mesh cards, changed the lighting but the splotches look the same. Not even switching to software Lumen changed much about the result.

Pathtracer:


Lumen:

Update:
I can change the result by blocking the window on the other side of the room: