Unkillable Monster

Was clearing a T3 Waystone as usual and nothing seemed odd during the run. About half way into it, I noticed my minions kept running back and so I followed them. They kept attacking this golem that would die and revive without anything else being nearby. It was a part of a Rare with the "Revives minions nearby" modifier, but I exploded all corpses nearby to ensure none of the corpses were the Rare's figuring maybe the game bugged out and didn't think the Rare was dead so it kept reviving it?? I dragged that golem along the remainder of the level killing it probably hundreds of times in the process..

https://youtu.be/D1JP203lBVk