Titan Grotto Boss not taking damage

When fighting the boss after he moves around to the far left position, he will not take any more damage. Also issues triggering him to change position due to not taking damage as he will not trigger to change position. Game breaking for some people.

Also getting this fairly randomly after he changes position. Only seen on a melee character so far for me.

I'm also experiencing this bug everytime I go for this boss. I'm playing a merc with a crossbow and a maul. Not sure what the trigger is but eventually, at some point in the fight, no matter what I use (though it seems to happen faster with the maul), ol' flamey titan boy stops taking damage. Game breaking and frustrating.