This was actually a pretty interesting bug.
Edit: fixed weirdness
So automatons share a drop table, but obviously need to know what type of automaton it originally was in order to determine which gloves to drop - to do this drop code switches based on the original automaton npc type and returns the gloves to give.
The problem occurred because when automatons use their special attack they actually change NPC type (e.g. automaton_magic_special). This is actually a very clean way of handling the special because the new npc config can handle the animation & forcing the npc to be stationary etc with less risk of a bug making it through (ironic I know).
So the bug ultimately occurred because the switch that handled rare drops didn't have cases for the special variants.The bug had actually been in-game since release but only became apparent when we fixed a separate bug a few weeks back that prevented players from getting duplicate cresbot drops.