Zalmarath, the Colossus

Sometimes, while fighting Zalmarath (act 2 normal), he becomes un-damageable. You can target, you can swing, but you will deal 0 damage for the rest of the fight and have to suicide to get another shot at it.

Also, his stun threshold is like 10000x times higher than any other mob or boss so far in the campaign and feels borderline impossible to kill as a warrior.

i just had this bug also. minions also stopped attacking. couldn't target with flammability

resetting to the checkpoint fixed the fight.

Just tried him and had a lot of trouble with him. First time I was in a three man party. A little way in, he stopped taking damage. Tried again same deal. Went with a duo afterwards, same issue.

Finally went solo with my Infernalist. I found that if I did any direct damage, he would bug out. Finally I was able to kill him by just letting my minions take him down on their own.

I am also having this issue, I've gotten very close to beating him, then suddenly he is unhittable, not targetable.