This may be an oversight, but when trying to complete a dungeon quest in a random queue, if the party is disbanded after it is completed, you are kicked out the dungeon and not able to turn the quest in.
It's always been that way they didn't design the activityfinderto work better because thereinstancesonly allow 4 players instead of maybe 24 in rare cases which then need adjusting so no one is kicked.
That would also fix the issue when someone is kicked or disbanded and a replacement can't travel in.
-PC (PTS)/Xbox One: NewBlacksmurf
~<{[50]}>~ looks better than *501
If you tell the group at the start that you are doing the quest, hopefully they will slow down and one player will hang around at the end long enough.
I do anyway and I've played with PUGs that are happy to do the same.
It doesn't solve the kick issue, but hopefully in most cases you can at least finish the quest.