Usually when i build areas or other things i ignore this however i really want this to be removed. The issue is that there is little spots of light in corners or at the sides of parts inside rooms. An example is shown below.
you have to make the walls thicker, it’s because of roblox’s voxel lighting system just being too low quality
make the walls thicker, or if the player wont be seeing the exterior of the building you can put a thick block that covers the entire thing.