Does it look something like this in creation kit?
If so, I had a similar problem that was solved by deleting all of the LOD files in Data/Meshes/Terrain (I just deleted the entire terrain folder, but you may want to check to see what's inside it first)
It looks (looked) exactly like that - I deleted the entire Meshes folder, to no avail.
Thanks to everyone who replied - I guess the bug mentioned was the cause and whatever we tried we couldn't automatically undo the issue.
Since the world we created is relatively small, we worked around it by surrounding the entire world with cliffs and then manually, painstakingly "softened" the entire terrain to be even. That caused f*kloads of static objects in the air or buried underground, but the alternative was restoring to a backup from 10 work hours ago... So we settled whatever we could back on the ground and a lot of stuff will remain buried forever.
I can't wholeheartedly complain when such a modding tool as the CK is freely provided, but s*t, Bethesda...
P.S., @h4vent - This is my first mod, I have ZERO experience with it. It's also a school project which I have no intention of using later, so I could afford leaving the entire world outside our small bit broken. If the creation kit Wiki was clearer as to the correct pipeline I should have taken, I would have. But it isn't. Whatever information there is partial, and the forums are little use to anyone who just starting. Anyway, this is the best way to learn
