check the WarehouseAmbushes interior cell (enable markers!) and the DefaultTriggers, there's one iirc DefaultActivateOnEnter or stg
also, check your trigger's ref, make sure collision type is l_actorzone or l_trigger.
the draugr need the MasterAmbushSCRIPT on them, the "ambush" property needs to be set to true.
your trigger needs to be the activation parent of your draugr (reason why you can't loot them will likely be you've already done that, but checked "parent activation only", uncheck that)
the coffin where the draugr is supposed to sleep needs to be it's linked ref. not sure right now about the lids, either also linked to the draugr with an additional keyword, or to the coffin (check warehouse example)
and the draugr needs a sleep package on top of his package stack (there's DefaultAmbushSleep package or stg, check any "ambush" actor), plus one that lets him attack (like DefaultMasterSCRIPT)
and the sleep package needs to be conditioned to actor value Variable01 == 0, and the other one(s) to = 1 (or was that the other way around... best also check any "ambush"actor's packages