Can't complete Graveyard map - boss won't spawn

I get stuck with nothing spawning in the Graveyard map in the boss arena after killing the second boss.

If I leave the game then re-enter my portals and come back, I can see the third boss but can't interact with him, moving mouse over shows nothing.

I have tried the map twice and had the same outcome both times.

I am a Freezing Pulse build with Herald of Ice so I freeze/crit kill the bosses, not sure if that affects anything.

I also can't leave the arena since the boss instance isn't complete so I have to either portal out or exit the game.

Bug report 2,783,813,782

Same thing happened to me on fire Twilight Temple boss except got stuck at 50% hp. It continued doing damage/skills but could not be damaged beyond 50% HP.

Bug report 3,833,136,222

Same thing happened to me in Graveyard - was in a "can't leave" Zana map, and the enemies stopped spawning in the Arena, and I couldn't leave. Bug report 2,807,388,301.

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