So I was just doing some arena and wanted to go back to do some missions, went to Jack Quicksilver to buy maybe a few items and here comes the weird bug:
I can tell him that I did all his quests and then ask "...now what" which will lead him to give me the quest to search for Azif in the Hanging Rat bar. Problem is I already did that quest so my best guess would be that after completing the quest it does not seem to delete that dialogue branch from Jack's response list.
Further testing reveals that I can repeat this endlessly without the quest appearing in my quest log.