Boss fight game breaking bug (spoilers)

Playing local coop and we just defeated Kategawa Jr. He comes down tried to hit us a few times and then screams and dies. Brilliant. But the it’s just stuck with the marker showing something on an upper level but no way to get there.

We figured this was bugged and both used the water and electricity to respawn and give him full health again and replay the fight hoping it was a simple bug but we did it again and the same issue occurred.

I’ve ready about him falling into stairs during this but this isn’t what happened. Has anyone else ran into this? Is there a work around at all?

TIA