Shenkay

I think you have to double read what Kaphotics post. Why? "restored my backup save file, traded back the Pokemon to my original switch" Pokemon Home make a Registration about where come from and where go to. So Your original Save have metadata, but now you are trying to return the pokemons that are transferred using a PokeHex. Pokemon Home could be detecting something abnormal on the HEX or Metadata of the pokemons that its not accepted anymore after the 3.1.2 update Now, This is not a 100% solution but, you can try use the Pokehex Encounter database create the birds there, Use the same PID and EC ID on Shinning Pearl and try to put the pokemon back to Home from the Shinning pearl game. But am not 100% sure will works but you can try.

Thank you for the post! This webpage/forum give me a reason for return and stay with all pokemons games again...