If you complete a delve, collect all the treasure. Then (still within the delve) you start a the Dawnbreaker follower dungeon (“join as group”), you will start the dawnbreaker dungeon, but will be trapped in the instance. You cannot hearth out. You cannot exit. If you leave the party, it says it will teleport you to a graveyard, but at the end of the 5 second countdown, nothing happens, and another 5 sec countdown is started. You cannot log out. I have repeated this bug twice. Only remedy seems to be alt-f4.