Bugged Mektul, the Forge Master

Was playing with a friend.
As a warrior, I leaped down to the boss from the bridge right above him.
This started the fight.
My friend then walked around, grabbed the checkpoint and entered the arena.
This forced the boss back to his state of hitting the wall while the lava crept up.
We ended up being unable to hit the boss and having to reset the encounter.

Tbf, maybe I shouldn't have jumped down there so that's on me. But, thought you guys might like to know :)

Cheers!