Lightmass created overlit surface

I’ve been doing some interior scenes, and when I build the scene, one of the walls gets wiredly overlit. Please advise. The lightmap resolution is in the red.

I have only one Hdri Backdrop. These are the settings of the inherited skylight.
What puzzles me is that all other object looks correctly lit, and all the other faces of this particular actor look great. It is only that one face.