Ok, I finally understood what happens: when you select the scissors tool, CC adds a (2D) polyline to the window. This mistakenly changes the bounding-box of the displayed entities (that's a double mistake because: first the polyline is not visible when the tool starts and second it's a 2D element, not a 3D one! -
I fixed this). Anyway the bounding-box is changed, and potentially greatly because the empty polyline line in its initial state is like a point placed in (0,0,0). This totally changes the depth-buffer normalization of the graphic card, which directly impacts the EDL render.
In your case, this glitch gave a better result. But that's pure chance, because in most case it worsens it... This issue shows once again that this depth-buffer normalization done on the GPU side is really the big problem of EDL. I've just found an interesting article on this problem here (I'll look at it more in depth in case it gives us a practicable solution):
http://outerra.blogspot.fr/2012/11/maxi ... e-and.html
