Launch issue Android

I’m working on an Android program (Samsung S3 Mini). When I use the Launch button to start the game on my smartphone, the first time I do it everything is ok, but if I change something on my blueprints and re-Launch the program, changes are not saved and the program is the same as the precedent version. So I have to close UE4 and re-open my project, and everything is ok until I change something else. What am I missing?