Problems with the Phaaryl Megalith Map and Deathlord

During the boss rush at the end of the Phaaryl Megalith map, the large sphere summoned by the Deathlord boss stayed on the battlefield after the boss's death. It stopped shooting projectiles but continued doing damage when stood in. It remained on the field during subsequent fights and after all the bosses were killed.

The arena also still disabled portals after all bosses were killed and the Atlas skill book was collected. Walking away from the boss arena re-enabled portals, but the claim that I was still in a boss fight and therefore couldn't use them was confusing. I think that this could be due to the sphere still being present, but it could also be unrelated.