I grounded mine pretty solidly to the chassis via a bolt, I don't think it oculd have come loose as a torqued it pretty good and used a nyloc nut.
The HU worked great the night i installed it and then the next day, then that afternoon i installed the update, worked great hten too...the day after (yesterday) it started rebooting on the ride home, thought it was the temperature, so i turned down the heat and it seemed to work, but today on the ride back to the apt it started acting up worse than before.