Crystal Ore Map Last Boss Bugged

I defeated 2 out of the 3 bosses in the crystal ore map leaving just the Champion of the Hollows but he is invincible and not taking any damage. Its health bar is stuck at about 80-85%.

Yep, also just encountered this on a juiced map. And my mate had it on City Square Map.

Same issue here. Ran in with a Delirium going and got all three of them to a little over half health and they are now completely invincible. Jokes on me I walked into the arena without picking up any of my loot in the map and now I lost it all lol.

This has happened to me several times on both this map and Wharf. IF you kill the boss and/or the boss adds too fast on both maps, the bosses become immune. Leaving the map and returning sometimes fixes it and other times leaving and returning multiple times seems to fix it.

This seems to specifically be related to killing bosses too quickly (and perhaps minions) with invulnerable phases where a race condition happens and the mob stay perma-immune.