The closest thing to a Bug I'd heard about with it was people "losing" their main story quest.
When you had more than 5 quests accepted it would knock some off the list ... and not automatically put them back on, so a lot of people didn't know/couldn't figure out to open up their duty list and manually add the quests that fell off back to the duty list.

I just wish there was a way to filter the duty list:
Dungeon :: This would show dungeon timer / requirements
FATE :: This would be if Leve information showed up in the duty list ... and have a priority place in the field (sometimes I want to leve-sync and finish my Leve after a FATE... but I can't)
Levequest :: Sometimes I've picked up Leves that I don't want to do right away (crafting leves I find good rewards on), this would let you shove them out of the way to get back to later.
Quest :: At this point the only quests I see are class-quests and relic quests... neither of which do I ever really need to see anymore. However if I turn off the duty list, I can't level-sync for FATEs, and don't have timers for Leve or Dungeon events.


Being able to manually sort the list would solve this problem for me... but having a toggle for each of these different type of events, or separate lists which can be displayed so they don't share the same space would be preferable.