Lock screen issue

[Edd7711]

When locked in standby, the screen sometimes suddenly turns on (as to show notifications, even if no new notifications are showing, and even if I deactivated the "wake up on notification").
Moreover, when I press the power button to wake up the phone to the lock screen, it doesn't always work: instead, when I press the button again the screen "flickers" (as if it received 2 inputs at the same moment, to turn it on and off).