My daughter updated her iPhone 6S to 10.1, since then she's had the phone shut off randomly as if it has no battery power left. The battery has been 80 to 90% sometimes when this has happened. Worse still is that it will not power back on unless a charger is connected to it, and when it turns back on then it is back to the same charge level. And all normal again. We've spoken to apple and they have run a remote diagnostic on the phone, no faults found. We need to get booked int a genius bar now. It'll be a few weeks before we can do so. In the mean time, does anyone know of a bug or setting in iOS 10.1 that could cause this?