Crushbone Slave Keys not droppable.
 

I thought I'd kill some orc slavers on a character that doesn't mind faction hits to give the keys to another character who does, but I just found out that Shackle Keys 18 and 19 cannot be dropped to the ground.

Either the keys are bugged and somehow can't fall to the ground or they are flagged as No Drop perhaps despite lacking the NO DROP tag.

All “key” items are pretty hard to drop. Otherwise, every time you tried to use them on a door, you would drop them.

You might be able to fill your inventory (perhaps by unstacking all your food and drink), then click the key onto your inventory’s class portrait to drop it.

You can put them in a bag and drop the bag but otherwise yeah you'd have to do something like Videri suggested with having no room and forcing them to drop to the ground

Ah damn, kicking myself for not trying the bag thing. But that sounds like it'll work, thanks all for the suggestion.