Zalmarath, the colossus immune

Command gas arrow on skeletal archers made Zalmarath, the colossus in Act 2 immune in multiplayer on multiple attempts at multiple player counts

Can confirm,, we had 3 people, and at random times during the fight he goes immune and no one is able to damage him anymore.

Ran into this a couple times this evening.

Experienced this consistently today. After testing for a bit, it seems that past a certain time, he suddenly becomes invincible and immune to curses, ailments, auras, AOE, etc. For some reason I am able to hit him with mana drain and he does get slowed from it, but nothing else seemed to affect him. The arena also breaks as if he entered the next phase of the fight, but he still uses his moveset from his current health (he won't do his eye laser yet or his attack where you have to hide behind his sword).

Can confirm. This happened 2 attempts in a row for me. on the third attempt it did not happen but standing behind his sword didn't stop me from being damaged on one occasion.

Having this happen at the moment and now cannot progress any further in campaign due to this bug. It is completely random when it happens, one time it occurred when I had damaged over half his health bar, other times when I have merely scratched his health bar.

Having this happen now and also cannot progress campaign because of it. Playing solo on a melee character.

Also happening to me.

Currently in the same boat. Playing Witch and 5+ times now he will go immune shortly into the fight. Unable to progress.

Having same issues with my Titan. When it opens its visor for the small projectile attack and changes its position I lose all ability to hit it.