The Grand Inquisitor got locked out of the arena at the end of the Light’s Refuge dungeon, causing the dungeon to be impossible to complete.
EDIT - Since the Grand Inquisitor is stuck outside the arena, I had to quit the game to be able to exit the dungeon.
EDIT 2 - after exiting the game it put me into a super long (~41 min) queue. Not sure what happened but it seems like it could be related to my issue.