nav 8.4 shuts off or freezes. shuts down climate system. Happens several times. Dealership didn't know why it would shut down or freeze and be unresponsive. I can not turn on heated seat, heated steering wheel, windshield defrost, change anything with heating or cooling. Screen was black. No radio, no sound, completely useless!!!! Only way I could get it to work was to shut off the truck and then restart it. This happens both with remote start and manually starting. Wondering if it is draining my batteries as well.