There’s a bug where after defeating the final boss people are disconnecting before the boss crystal is broken. It registers as the quest being finished from the standpoint of not being able to run it again and counts toward titles, but you miss out on all the loot, most importantly the darkstones. No telling when you are going to get disconnected, and the workaround of not skipping cutscenes works sometimes. Deleting and reinstalling the game doesn’t take care of the issue.
Converse with fellow players