I’ve gone ahead and circled the problem areas for you so that you can work to narrow down the problem
Red: Light coming straight through the backfaces of the wall, either the mesh is too thin, is single sided, or there is some other problem
Green: Striped issue, generally a distance field problem (common with two-sided distance fields) or like I said, intersecting lightsource. But you say that isn’t happening here so…
Pink: Hole?
If you can clean up the scene to get rid of those issues, Lumen should behave better. With regards to the distance fields I would suggest checking the global distance field debug view, and make sure you aren’t using two-sided materials or generating two-sided distance fields.