One of the guards outside of Understone Keep sometimes has their feet sink into the ground.
The marker (00036F8D) seems to be the one where it happens often. I think maybe I've seen it happen to the other marker (00036F8E) before, but maybe I'm mistaken on that. It's possible this could be one of those weird engine bugs with AI markers. I can't see anything clearly wrong with the placement, but maybe you can see something I'm missing.
Screenshot:
https://postimg.cc/bDtgKpgP