@tig said: If it happens with just a few faces it could be z-fighting where there are coplanar faces inside groups etc and then the display has to decide which material to show, and it varies depending on the angle - this is fixed by either erasing one of the clashing faces or moving one a few mm away from the other so it doesn't happen... That's what I would think, too. See attached example. [image: 8dOh_z-fighting.png] z-fighting.skp