On the very large bases I have, npc will just walking through the foundations/walls of the base they spawn with and end up "under the base" before walking back out at some point - as if the bases wasn't even there.

I'm guessing this is a bug with the npcs' path finding/collision detection and I'm not sure if there is anything that can easily be done about it.

known issue just haven't gotten around to fixing it. also a duplicate thread ^^