Trial of Sekhemas Third Trial Boss Jumped out of Arena, Unkillable

While fighting the scorpion trial boss, it entered the underground phase. I ran towards the top of the arena near the exit and it jumped at me and landed on the other side of the arena door. It then exited the phase on the other side of the arena door in the chest room and started pathing further and further away from the arena. Boss is unkillable, and I'm locked in the arena.

Bug report reference number is 3,143,105,065

Relogging allowed me to refresh the instance and reset the fight, in case anybody gets this as well and panics.