NPCs forget where their place in the world is
If I move an NPCs by attacking them and making them follow me, then go and pay the price for my head via the thieves guild, return to the place where I attacked the NPCs, then they initially try to go to their original place (it's OK), but if I save and load at this moment, they no longer intend to get to their original positions and stay fixed at their current place forever. Used this to easily steal a lot of stuff that is otherwise is not easy to steal.
Tested in interiors with NPCs that don't walk around (i.e. their behavior is to stay in the same position).
(RM-3656 from redmine: created on 2016-12-13 by Mark Karpov, , closed on 2017-06-20 by R. D.)