I also encountered this bug. The red line marks the line of contact between the building and the extension. I was able to build an extension in such a way that it was not a street for the game. To do this, I broke down all the contact walls and built a box, then removed the excess for the doorways. The game began to perceive it as like a house within a house. The light is behaving incorrectly.
Further: 1 - the original building, 2 - an extension.
The screenshots show how a dark cloud appears in place 1 if the character is in 2
When moving from 2 to 1, the all environment is darkened, just as the environment is darkened when moving from the street to any building. Only now the dimming is 2x.
If the character is in 1 and the lighting is turned on in 1, then front of the character the boundaries between the environments are not visible, but shadows appear on this border behind the character's back
