Summoning Circle inside Ritual created unkillable Boss

There was a Summoning Circle inside a Ritual space. The Boss that was summoned was "Chetza, the Feathered Plague" who spits out a secondary Boss, "Plagueling" upon reaching low life.

Since the Boss was summoned inside the Ritual space, once I did the Ritual, the Boss spawned again. While Chetza was killable, the Plagueling that got summoned was untargetable and did not receive any damage. The bug was similar or identical to the recently fixed bugged minions in the Vaal Temple.

Leaving and re-entering the map, therefore forcefully ending the Ritual encounter, was the only way to proceed. Later on in the same map, when I did another Ritual encounter, and the Boss got summoned again, the same issue occurred.

Here is a steam recording showing the bug:
https://youtu.be/Uu1lBRBbJZo