... instead of sleeping inside.
So, in my mod, I've put draugr with creature alcove markers inside their sarcophagus. When I load a save made before installing the mod, the draugr stand at their markers, outside the sarcophagus. The lids "explode" normally when the player crosses the trigger.
(I know for sure that everything is done properly, since when I test it with a save made after installing the mod, the draugr are inside their sarcophagus and they pop out as they should when the player crosses the trigger.)
This place being filled with people used to deal with bugs, glitches and the like, I'm asking you: "what's going on?" And what can I do to fix this, since I cannot ask future users to create a new game to play my mod.