I am just starting out in Unreal Engine, and I bought an environment pack off the Marketplace to get some practice. When I do a lighting build, I get mysterious dark spots on a mesh surface (brick wall and windows). I searched around to see what might be causing these spots, and learned a bit about Lightmass. I set up a Lightmass Importance Volume. In addition, I adjusted the Static Lighting Level Scale to 0.5 and the Indirect Lighting Quality to 2.0 (based on suggestions from a YouTube video). I set the Num Indirect Lighting Bounces and Sky Lighting Bounces both to 10. Finally I adjusted the Indirect Lighting Smoothness to 1.2 (again based on YouTube). Overall, the scene looks better BUT none of this made the dark spots go away. Any suggestions to fix this?