does a nodraw brush have a shadow

[Psycho[BE]]

in my latest map, my surroundings are alle cliffs made with displacement maps, but to seal my map form having leaks I made some nodraw brushes behind it. In the 3d view you can sometimes see a part of the nodraw brush instead of the top of the cliff. if i compile it the places were the you see the nodraw-brush in the editor instead of the cliff, i get shadows on my cliff. what could cause this?

 

[Stigmata]

From my experience about six months ago, they do.