There are a lot of copies floating around out there of the newest Pokemon release. However, it’s not all going as well as some players would look. A number of people are reporting through social media that the game is being corrupted when they save in Pokemon Centers. There’s no real pattern to it or reason for it as of now and it’s not happening to everyone.
Game Freak is aware of the situation and I would believe if there is a fix needed that one will be on the way soon. Until then if you want to make sure your game continues to work don’t save while you’re in a Pokemon Center. Make sure you save before or after you go in the building.