Board Thread:Questions and Answers/@comment-66.108.6.230-20150728195139/@comment-26215551-20150728201322

Just making sure, the swords you're trying to put into the party aren't the leaders of any of your other parties, right? Because they can't leave the leader slot. If not, and you're sure that they're not on expedition or being repaired, I would try closing the game and reopening it - it might just be a temporary error. I think that worked for one other person who had the same problem.