Reported by a user:

Hello Stephanie. I have encountered a bug in the app related to all of the pokemons within the mr. mime line. Whenever i try to right click any of them, to mark them as “transferable” nothing happens. It seems like that specific line is unable to be right clicked. idk if any other pokemons have the same issue, but so far i’v only encountered it with the mr.mime line/regional variants.