(FIXED) How to prevent area from generating navmesh?

[RWild311]

Hard to see in the image I think but between my outpost and the holy mines there is the prayer day up on that mountain, in game you would see it is impossible to get there but this spot keeps generating navmesh so homeless spawns keep popping in up there especially if I unload the cell and come back.
I tried putting rockes up there which blocked most of it but I can't fill every tiny little gap so someone will almost always spawn up there anytime I move out of the area.
Is there some building or map object I could hide up there that would completely stop them spawning or just block all navmesh on top of this mountain? I've tried placing an empty town up there but somehow they still went there so I guess it must have no navmesh to prevent this?

[Bookhorse]

Weird, can't say I understand what's happening. :\

[RWild311]

Seems to be fixed with 1.0.35 update.