In some phones when screen is locked then the app reestarts!!

[mcr222]

It might be due to the saving energy the phones do, that they just turn off apps that are on the background. Our app only requires a thread listening to the bluetooth when working (there is actually one thread per user). In some phones this feature can be deactivated and then the phone does not shut down the app, but in others it might be possible (it has to be investigated).