Firmware: 0.9.5
In my configuration, I have the cabinet light on by default, with a timeout of 30 minutes. When I first start my Carvera, M821 and M822 behave as expected: they turn the light on and off. After the 30 minute timer expires, M821 will turn the light on for less that a second, then the expired timer shuts the light off again. Using M821 should reset the inactivity timer.