Vaal Temple - Golden Forge - Second boss stuck underground

I was clearing a Golden Forge in my Vaal Temple. It spawned both the forge boss and Xotalan, high priest.

I killed the first boss and Xotalan is now stuck underground, I can hit him (and it will trigger the boss lifebar to show up), but he cannot take damage and I cannot complete the room.

I've left the temple and re-entered but it just remains in the same state