Achates bug taking no damage

Hi there i just encountered a bug that i didn’t witness before. I’m Tier 3, 1367 and i always help people during the night to clear it. Today i died to Achates because it was taking no damage at all. The damage meter was showing as if i was doing damage to it but it wasn’t dying. Everyone in the party died before me obviously and i had used all my pots trying to survive this bug. Was frustrating but funny at the same time lol. What’s worst was that when the raid failed message showed up, it said it had more than 80% hp on the 2nd phase (just before he starts the the statue phase).