I have an iphone 5s and recently I had to replace the volume flex cable which after undoing all the phone and putting back together was a success, then I had my brother sell it to someone and a day later he came back with the phone showing the phone only boot to a white screen with black apple logo that stayed on with his finger still pressing down on the power button for around 5 seconds but then went to a blank screen but the phone still turned on then about another 10-20 seconds it turns off completely, also when removing finger off power it instantly goes to a blank screen. If anyone has an idea or a solution that would be great! :*