Hard to see from a quick look at your code,
But.. what you describe 'could' happen when you have two exactly the same entities/meshes at EXACTLY the same position and rotation - but with different materials/brushes.
Sometimes you'll get a nasty noise on the textures or material flipping like you describe because the camera doesn't know wich entity to prioritize over the other (cause the polygons occupy the EXACT same space-but with different attributes).
So, I can imagine that you somewhere accidently create 2 copies of an entity without knowing it, or forget to move one away. Especially since you say it seems to happen when the camera angle changes....
Hope this makes sense, not sure if it i'll help in your case..
D.
But.. what you describe 'could' happen when you have two exactly the same entities/meshes at EXACTLY the same position and rotation - but with different materials/brushes.
Sometimes you'll get a nasty noise on the textures or material flipping like you describe because the camera doesn't know wich entity to prioritize over the other (cause the polygons occupy the EXACT same space-but with different attributes).
So, I can imagine that you somewhere accidently create 2 copies of an entity without knowing it, or forget to move one away. Especially since you say it seems to happen when the camera angle changes....
Hope this makes sense, not sure if it i'll help in your case..
D.