Came here to make a topic regarding this, as another player told me it was not DR, but rather the game bugging and not recognizing that you had tagged the mob.
It’s happened to me probably a total of 12 or so times throughout Halloween (I’ve been grinding the lab a LOT) and it’s occurred on all 3 big bosses.
Just finally ragequit and came here to seek confirmation of the bug after dropping a Viscount, Lich and 2 Horrors, all 4 with absolutely no corpse loot.
It seems like a silly thing to get worked up about, but those bosses take several minutes to down and once the chest is done the corpse loot is all you get for that time investment. In the case of this last run, that’s 25-ish ToT bags I’m short from missing out on those Large bags. Considering once DR kicks in it’s basically a porous bone-fest in there, and I’m a relatively new player who could really use the loot, it’s really bugging me to have this issue so consistently