Robalo

Do you do them in paint? If you do, be sure to reduce the work area around them so that it is as close to the sprite as possible. I think that this might be your problem, but if it isn't, then I do not know much else .

Actually, having the Beldum holding the Everstone would have no effect. In matters of Everstone breeding, only the "mother" can pass its nature. In normal breeding, the female pokemon is the "mother." But when using a Ditto, it is always the "mother," so the Ditto would have to have the correct nature.