Mäxl

Hi, I think I might have a kind of game breaking bug. It doesn't crash the game or anything, but basically makes it unplayable, and I simply cant find the reason for it. Some of the houses I enter are partially or completely dark, that means no walls, objects or anything else is visible, only the NPCs but they stand in a black screen void. I added a picture of my in the first gym for example. Does anybody know what causes this?