I was just now in a group for Twilight Arbor story mode, got to final boss, someone left so I zoned out and went to Lion’s Arch to find a 5th. Came back, and when I attempted to enter the instance, I and the person I found were put into a freshly spun story instance, with the npcs waiting for me to trigger them. The other 3 members were still staring at the boss. The typical tricks of logging out and back in or logging into alts and back failed, there was no ‘join in’ option, and when the other 3 zoned out and back in they were also put into the new instance, forcing us to start over (actually we just quit)
The person who left was not the instance owner, and I’ve been able to zone out and add replacements in before, so something went wrong here