Hello (sorry for my english^^)

I have a problem with created NPCs. I have worked in an existing WorldSpace (build a house and tower) and set there some NPCs.
If I travel there the first time everything is ok, but if I enter my house and then leave it some NPCs are disappeared, some are in another place and some stay where i wanted them to stay (or move/do action).

Does anyone know how to fix this problem, it also happens if i travel to my house again from another place.

Greetings Nephilim