If a player updates the app (e.g., v3.2 → v3.3) but the cloud save is from an older version, the game may reject the save data until a migration script runs. If migration fails, data appears “lost.”
The game does not autosave to the cloud after every single action. It saves periodically — usually after finishing a level, making a purchase, or when you quit the app properly. angry birds 2 save data upd