CPU usage on top hovers around the 2~6% mark most of the time. Xorg and browserd are among processes that are most active. Afraid I'm quoting this from crude visual inspection. Is there a way to log the top output?

As Estel said, the problem appears to be that the device just doesn't want to sleep. Here's a wild shot - could it be that the sensor/trigger behind the lock switch was somehow damaged during the time that the switch was broken and exposed?