Arbiter of Ash bug

A friend of mine placed the 3 fragments in the burning monolith. He died and left the arena and i finished the boss, then he came back in right as the boss was falling down on his knees. The arena then was filled with petrified corpses and there was a quest item on the top left corner that we could not get to as the path was locked in a straight line from the entrance to the throne. One more thing, as my friend ported in the arena after he died i got ported back to the entrance of the arena and thats when the arena got the petrified corpses and the quest item appeared which was not accessible.

I had a similar thing just happen to me, just as I killed him i died and when i respawned due to the new 6 attempts for the fight the bodies were blocking the quest item to finish the burning monliths quest line. If there is any fix for this it would be much appreciated.