Lets make Lightmass EPIC (and understandable)

Hi guys! Been following this thread for a while, and got amazing insights here on how to work the lightmass.
Nonetheless my adition is not so magnanimous.

I’m having some blotches showing up after the bake and I can’t figure out why. Increased lightmap resolution, verified UV’s, baked in production, but I’m still stuck with same problem.

Everything else seems to be ok (light is too strong and burning quite a lot)!

It’s strange cause I already used this model in previous works and never had this problem. Also the wall should be complanar and the shadow much smaller.

Is this due to indirect shadow?