Quote from Essentia:
I just found a way to save ~10 seconds during the cutscene where Melchior repairs the Masamune. First, put Lucca and Marle in your party, then use the fadeout glitch to skip talking to Melchior when you first enter his hut. Then when you go downstairs to repair the Masamune, Lucca will remain in your party and it'll skip all of her actions and dialogue. This saves time by not having to wait for either Lucca or Robo to walk around, check the books, pick up the cup and rock, or say anything at all. Also, for some reason Robo gets put back into your party afterwards.
that´s very good tip, just tried it out today and saved some time.