I'm rendering planets using a couple of UV spheres (terrain and atmosphere) and a displacement node (for mountains) in Cycles. Since I've upgraded blender, sometimes the renders have square-edged artifacts as you can see in the image below.
It almost looks like it's not respecting the
shade_smooth setting on the meshes. But the size of the artifacts is larger then the size of the segments of the sphere (and way more then I'd expect the subsurface'd segments to be.)