Unable to hit Forge boss

It's the giant you fight in act 2 in Titan's Grotto.
My character is unable to hit him using any attack.
I can't exit the arena, and exiting to character screen brings me back to the same bugged fight. I can't portal out - is there any way to reset?

Bug Report ID: #107455522

It just happened again, is this fight bugged now?
Bug Report ID: #2888652564

Is there any way to solve this?
Can't teleport to another player, can't get invited or join team, can't exit map as restarting brings me back to it.
I can't kill him, he can't kill me :O

Bump - it's happening again. I can kill the boss, but it takes a while sometimes before the hitbox becomes active.