There was the bug, that if the device was put manualy in standby and the power management settings had set time the both for standby and for off then M92 switched on after some time. Or it was something like this. Power management instead of doing nothing or switching off switched on.
It should have been fixed some time ago, but it seems to me that sometimes it still switches on, but I am not 100% sure if it really happens or it is just my "feeling"...