not sure if I'm doing something wrong or if there is a problem with my N4... When I am in a call (normall call or skype), the screen turns off after a few second, which I assume is working as intended. However, either during the call or after the call, when I hit the power button to bring up the lock screen, either nothing happens and the screen stays turns off, or the lock screen flickers on for a brief second, then turns off again. This problem persists for about one minute after a phone call, then the lock screen turns back on as normal again.