UE-22652 is unfortunately a limitation of the platform. There is no such concept as “quit” on Android. The Event shutdown won’t get called by killing the app. One way to do this for Android is to save the game on pause instead. Another way to go is to put in a save game button, but pause is easiest. (paused fire off if you hit home or the pause button) I hope that this information helps.
Make it a great day