Two years ago when I was working on Waterdeep I would get mysterious floating evil dwarves and deleting them would cause havoc - delete some prefabs in the area or even crashing. Today I finally solved the mystery! You can not create a prefab with a door in it. The doors must be added later. Try to prefab with a door and you will face the wrath of the evil dorf!
In the extremely rare chance that you see this happen...just select the dwarf and detach it from your prefab group... then you can safely delete him and send him straight to the nine hells!
