In my HL2EP2 map, I am trying to make a sewer using a half of a cylinder (screenshot below) but it is giving me these black textures on some of the surfaces. In this screenshot I pointed a flashlight at each of those textures (for the one's wondering how I kept the light of the flashlight there, just type "create_flashlight" in the console)



To avoid confusion, The wall in front of me doesn't have the bug, that is just some bad light placement of mine.