This may just be a limitation of how it works. What happened is that I had the limestone mine designation inside the larger one I was using to flatten the mountain it's under, and after i had mined past the border of the other one, I noticed it left a terrain ghost behind. It's a purely visual glitch since the designation is still where it's supposed to be.
Reproduction:
- have another mining designation inside another, specific purpose doesn't matter, only the borders here.
- Dig under it, just a level or two would be enough, wouldn't need to be as dramatic as this one.
2a. Optional: Fill over it, I haven't tested that, but you may have the same thing with fill. - Look at the mining designation in designation view.
- Select the mining tower that designation belongs to and select edit to update it to fix it. No actual editing needed, just needs that update.
