Flickering curved floor corner above basement.

This has never happened to me before! After building a basement I noticed that the ground above the basement was flickering, just in one spot - next to a curved fence corner. At this point I filmed the following video to illustrate the issue: https://www.youtube.com/watch?v=bQWU3WXr2zQ

I quit the game for the night and loaded it up again this morning. Now huge patches of the basement ceiling were missing, causing the ground above the basement to disappear! I added the ceiling back and the ground reappeared, no worries. But after doing this I noticed that ALL of the floors next to curved corners were flickering! In the first video you can see that it's only that one spot, but it's spreading like a rash!

I have searched this forum and google for answers but haven't found anything. Though maybe I worded it wrong? I tried searching for "flickering floor above basement" and "curved floor flickering". Has anyone encountered this before? Any advice would be appreciated!