Suggestion: Add a warning to the Memorial Dungeon craft NPCs
The old Socket Enchant NPCs had a warning about carrying multiples of the same type of item:
mes "[Seiyablem]"; mes "Oh, there's also something really important that you should know."; mes "If you ask me to add a Slot to something, make sure that you don't have multiples of it in your inventory."; next; mes "[Seiyablem]"; mes "Here's an example: if you have a +7 Manteau and a normal Manteau in your inventory, then I will randomly pick one of them for my Slot Addition attempt."; mes "Just remember to be careful."; next; mes "[Seiyablem]"; mes "Again, ^FF0000only carry one of the equipment to which you want me to add a Slot^000000."; mes "All other equipment with the same name should be placed in your Kafra Storage, got it?";
I suggest adding a similar warning to all the current and future Zero crafting NPCs that use equipment as an ingredient.