Why did my Pokemon only breed when I moved the Everstone to Ditto?

Question

For context, I'm trying to get shiny Alolan and Galarian Meowth in Pokemon Violet and decided to throw in a Tandemaus in case I get lucky with a Fo3 (My party in the Picnic was Ditto, both Meowth forms (both female), and Tandemaus). I used Egg Power 3 to gather eggs.

• My first attempt at gathering eggs, I had both Meowth holding an Everstone, Tandemaus, and Ditto, and I got no eggs.

• The second attempt, I removed Tandemaus thinking it was the problem with both Meowth still holding everstones, but I still got no eggs.

• The third attempt, only Ditto had an Everstone, I brought Tandemaus back, and I got eggs from Tandemaus and both Meowth forms. However, the eggs I received from the Meowth forms were all Kantonian.

I know having both Meowth hold Everstones caused nothing in the picnic to breed, but why? Why didn't I get any Tandemaus eggs? Is there a way for me to get Alolan Meowth, Galarian Meowth, and Tandemaus eggs all at one time, or do I have to breed them individually?

Comments

Well the Meowth from the eggs are all Kantonian. Dang it.

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You didn't get the "they prefer playing with other Pokemon" message, right?

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I reworked my question to make it more coherent. This is Gen 9 where you use picnics for breeding, so there is no message like that.

With picnics, if you have multiple Pokemon in the party that can breed with each other, you can get eggs from multiple pairs. With my party, in theory, all Pokemon should have only been able to breed with Ditto. However, I got no eggs when both Meowth held everstones, even though both Meowth are female and Tandemaus is genderless.

You get eggs in batches of 1 through 10 when you check one of the baskets in the picnic. Egg Power 3 ensured I would get eggs quickly (as I did with my last attempt), but with my first 2 attempts at collecting eggs, I went several minutes without getting eggs, even when checking the basket periodically. So I can confidentiality say both Meowth holding the Everstone caused Ditto to not breed with anything.