Abyss can spawn in boss room

I just ran a Molten Vault map and the abyss spawned in the boss room with the forge master. I am unable to grab my loot from the abysmal trove and the loot from the killed enemies since the hardened lava stops you from walking anywhere.

(Series S)
I had this happen to me earlier too. It was on the graveyard one with Draven. I don't know what the loot situation was like, I died 😂