Sometimes when I open an app suddenly the apple symbol shows and phones gets locked and I have to enter the passcode again.
I have an iphone 6s Plus, with I.O.S 9.2.1 and Sometimes when I open an app suddenly a white screen with apple symbol shows and phone gets locked and I have to enter the passcode again even in my setting I have set to ask passcode after 4 hours.
iPhone 6s Plus, iOS 9.2.1