You have to reset your AF quests in Jeuno and redo AF1 (weapon) and start the AF2 quest to be able to pop a coffer for your regular AF again. Might have to start the hand quest in Upper Jeuno as well. No1 is really sure about this.
If I upgade my Myochin Haidate to this +1 version can i still go bk to Quicksand Caves, pop a Coffer and get the reg bk? I'd like to keep a pair for capped missions.