The manipulated brush in the 3D view looks like an invaild brush..
You should split it in 2,, and one of the brush parts could be formed like a triangle, instead of making it "all in one".
Or did I missunderstand something? :S
Example:
and the red circle shows a spot where I think the brush is diagonally misshaped..
I don't know about that one though,, it might be the camera.