My Libra sometimes is upside down when I use the sleep cover, because it takes a few seconds for the sleep cover to put it to sleep, so if I put it down at an angle, it can flip the book upside down and then go to sleep. I never see this when I use the power button, because I'm always holding the Libra upright when I press the button. I'm not sure how your Sage can flip the screen after you've put it to sleep already.
