It wasn't a bug. The perk states three precision [b]shots[/b] will reload your mag. Not three precision kills or hits which means it was working as intended. You can shoot Superman in the head all day with a sniper, but he's immune. Its still a head shot. Unless its kryptonite or a magic bullet, it wont harm him. It's a precise shot whether the target is immune or not. Imo, they could've fixed oh I don't know, restoring the hive major damage to the Black Hammer like it's supposed to be...unless the extra damage is already included. But there's no evidence of such extra since the perk isn't there.