Zalmarath the colossus immune to damage

When playing through the storyline (Act 2) with 2 of friends we all experienced Zalmarath the colossus being immune to damage.

We are unable to kill him now after several attempts because he becomes completely immune to all damage for 5+ minutes before we either die or log out.

I'm pretty certain that the issue occurs when the floor breaks, as each time we have tried this has been the case.

None of us have experienced this issue prior to the recent large update.

Please fix this issue as we literally cannot progress the storyline due to it.

literally just rand into this on cruel difficulty on my witch. emergency patch cause this stops progress for sure lol.

Same happens to me. This hitbox is so bugged

I tested with my friends and if he dies before the floor breaks then you can progress.

I have a high level character if you need a carry for the fight to progress?

I've encountered this before on my sorc while playing with others. Now today, while playing my hard-core witch solo in cruel mode...the colossus became invincible at approx 15-20% HP. My minions and I are unable to target the colossus boss what-so-ever. The minions don't even attempt to attack him...they cannot "reach" him.

Now, when I log into my hard core witch, I'm stuck in the arena with the invincible Colossus.

Please fix this bug and/or reset my instance so that I can continue playing my hard-core witch.

Reset at checkpoint 4 times on this character and boss keeps going immune. I am running infernal cry, armour break scavenging plate thorns in Act 2.

This bug is still in the game. A boss becoming immune to damage is kind of serious.

This just happened to me three times in a row in a mapping zone. I lost 30% of level 82 because of this bug. Please fix this. I'm already struggling with the absurd 10% experience penalty for deaths over lvl 70. I don't play hardcore for a reason and this makes it very hard for me to enjoy the game if a few deaths to bad mechanics or multiple named stacked to top of each other costs me hours of progress.