Magatama Crafting Guidance

[Suikoden]

I try to use magatama crafting to the best of my ability but have trouble since every time I craft something, the grade goes down. This makes almost anything I make useless. I upgraded her all the way to 18 and she still hasn't changed a bit in her skills. Can someone explain to me how to make better use of her? Or is this all luck based and each time she crafts it, it will always be worse. I mean come on, there must be a way to increase it like smelting. It can't just get worse and worse whenever I make it. I need an understanding of how to perfect this.

[Tekato]

It's just rng nothing you can really do besides level up kaguya and hope she doesn't troll you