Local Storage bug?

I have a game in the google play. There is a save system (local storage). As long as the players are playing on the current version, everything is fine.

But let's say I release a game update on the google play and players click "Update Game".

When you first enter the game after an update, sometimes not all saves can be loaded. The second time you enter the game, everything will stabilize.

What could it be?

Could be something to do with variables that you only do on first launch of the game. The save data will still be there but when you load the new app the variables won't be set yet. It makes sense that they would be set when you load it a second time. You can test it yourself by clearing local data and launching the app as if it was the first time to see if you can recreate the issue.