Hi what can cause some random behaviours in my dungeon?

I have some draugrs that should sleep and a ghost that shoudl appear only at a certain time , instead sometimes they do work and some others they do not in the sense that the draugrs are standing instead of sleeping and the ghost is too instead than reanimate from a sitting position ....

why is happenig that? the only changes I can see is load and reload a savegame pripor to enter the dungeon and sometimes they do right some others not ... why?