You have to be very careful when the two buttons (power and volume buttons) is pressed because you have to make sure you press both at the same time it is very easy just press one of the buttons instead of two of them and if so, the effect can be both off the smartphone (if they only pressed the power button) or decrease the volume (if you only have pressed the volume down button). The conclusion is that sometimes you just press one of two buttons can happen so you end up doing anything but taking a screenshot of your meizu m1 note.