The firmware of this printer is very buggy - the message comes up every few days even if it was guaranteed to be switched off with the button - it also switches itself on spontaneously now and then or brings up the blue crash screen with an error code - the switch-off sound is choppy etc ... but it prints very well

Unfortunately, it also switches on by itself. And in the middle of the night.

Yes, first switch off (press the button and wait for the message) and then disconnect the power cable.