Pokémon Home has a "hidden tag" system that basically auto-deletes any Pokémon inserted into HOME that has the same tag as another Pokémon already uploaded to the server.
This seems to have the purpose of preventing cloned Pokémon from populating the system; however, the hidden tag is only applied to Pokémon upon the moment they first enter HOME, so cloned Pokémon coming from previous Generations, or Pokémon that are generated in (at the time of writing) Sword and Shield and never entered HOME before, are not detected by this system.
This counter-measure leads to an unintended effect: if a Nincada that accessed HOME and then a game able to communicate back and forth with the system then evolves, it of course becomes a Ninjask and, if requirements are met, generates a Shedinja; however, these two, coming from the same Pokémon, therefore count as having the same hidden tag, and because of this, if both get deposited into HOME, the one that gets stored second gets deleted, because the system erroneously thinks it's a clone of the first.
6
0