Hi,
In general world quest objects- like magic circles, demon circles and pillars- are shared among all players in the channel. Its hard to say whether the lag is what causes these objects to lag out and not disappear; however, I feel it would improve gameplay dramatically if these objects were instantiated for any player on the quest individually. Nine times out of ten these quests get stuck, making it unplayable. Especially when the mission is a mainline story mission.
A second quest bug to note:
Sometimes if two party members are in the same quest line it can bug out. In short, If person A takes the quest and starts doing it, it will complete it for them. Then as soon as person B grabs the quest it will show the status as completed, not letting person B actually turn in the quest or do the objectives.
Thanks