In IOS 12 on iPhone 6S. My wife's phone is in DO NOT DISTURB mode, locked and on the night stand while we sleep and will get vibration (notification?) And screen lights up. There is nothing in notification center. No messages. No attempted contacts from favorites. Can't find any sign of activity. Can happen several times during night, never at the same time c Shouldn't matter whether "vibrate on silent " is toggled since in DND mode. Can anyone help?.