This is a repeatable error where killing the boss too fast after entering the boss room can cause the game to not progress to the next wave. This also results in no rewards spawning nor the portal to teleport back. This is repeatable with any boss and typically happens if you kill the boss before the first "boss damage objective" spawns.
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Thanks for reporting. The team is already aware of this issue and is now being investigated.
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It's probably the shrieker and shank during early rounds.