My question wasn't about "the easiest way" -- I'd like to understand why this happens. If the reference mentioned above makes a difference, maybe I'm misunderstanding the slot_type_set tdesc when it says "A class defining a combination of object slot types" .. the objects in question do not have slots themselves and if it's about valid slots they can use, the name of that particular one does not seem to have any relevance for the base game, but who knows. I'd like to not make any assumptions here since it obviously refers to stuff I cannot test myself.
