swipe during bootup can hang UI
when i booted up the phone, i was cleaning the screen and due to the swipe up from bottom edge at a odd timing, the UI was stuck at notifications, no amount of swiping double-tapping changed anything.
i very briefly saw lock screen, but it was only a fraction of a second... no idea if this is reproducable or not.
Anyway, i got out of the situation, by pressing the powerbutton to turn off screen and double-tap to wake it again.