When using mirrors and staircases my screen will start having black flashes

If I'm building a house with a foundation or staircases (using a small staircase with a foundation) and a mirror (from what I can tell, it's any mirror, happens even when I switch to other types), black shadows will appear on my screen. The shadows almost look like the furniture I've used on that floor. I've been able to fix it by just not using mirrors in my builds when it happens. I have no mods downloaded. This may have already been posted, but I wasn't sure how other people may be describing what they see, so please let me know if there's any simular issues that have been posted. I would really like to use mirrors in my game more! You can see the flashes once you move over to live mode. From what I recall, I haven't noticed them when I'm still in build mode.