Quartz Stairs lighting glitch

Image 3: When I place quartz stairs on the ground, they present odd lighting on them. When I place another quartz stair on top of the previous one, it looks fine.

Image 2: Quartz corner stairs also show a lighting glitch

Image 1: Also, when placing corner stairs in a dark room, they also show a lighting error in the form of a shadow.

(for some reason attached images appear in reverse order of how I uploaded them, which is why I describe them in reverse order)