Altium FPC bending / bending line contains strange graphical artifacts

[smoothVTer]

I have a FPC wiring harness I've designed in AD16:



I define a bending line, and when I hit the '5' key the FPC bends but contains strange artifacts, as if bubble gum is being stretched between the edges of the FPC:




Anyone have an idea as to how to fix this and remove these artifacts?   Could it be some misaligned layer in my stack?   

[DutchGert]

You also need to set the bending radius