Trial of Sekhemas 3 boss (scorpion) got stuck past the exit door and was untargetable

Trial could not be continued as boss encounter was perma stuck. Boss disappeared, then reappeared past the exit door (kinda partially clipping into it). Attacks could no longer hit the boss, and the boss took no more actions. Trial dead!

I've had this happened before.
Best solution.
Click character selection. It'll save your progress right then and there. Meaning all hits you had taken during the fight before the bug. Then reclick your character, and you go back and fight the boss starting from the beginning.