How about when we recently (less than a year) started looting two hearts or two potions from the same beastie by chance? Could it be that those have something to do with each other?
I can't say no for sure, but I suspect they are unrelated. It's been reported by a player "double" death events happeed for players too when fighting with NPCs (and if the NPC looting capability would have been enable you'd have been looted twice too

). My guess is an extra double looting session is generated as a consequence of 2 death events happening not the other way around. Anyway I hope the engine guys can take a look at the open ticket in the bugtracker.