The Black Barya Boss disappeared

And another 3 940 094 772
Boss never came back

Happened to me too, so frustrating.

Bug report id: 1.710.060.053

The black barya boss disappeared during the fight.

Repro steps:
1. Go into The Black Barya
2. Fight the boss
3. Reach the phase transition where he does big aoe
4. Go to the stairs that lead to the outer ring
5. Wait for the boss to do the mechanic
6. Notice the boss disappeared

Repro rate: 1/10

I know that the boss is still alive because I still have 1 monster remaining in the top right corner.