Factory reset the phone and that should resolve it and when you log in back, set up fresh without using the backup. Manually login to your Samsung account and install the apps that you use. That way your contacts and important data will be there and ...
That's a good proof. Also, while receiving you can just say if the device is working at the moment. The issues like restart doesn't come up at that moment. So signing doesn't by default qualify for dismissal of the argument that the device is faulty....
