I have a 2013 Model S. For about a month now every few days when I start up my car the volume is loud and won't adjust. With either the scroll wheel or the touch screen I can see the volume level change but the actual audio level remains constant. To fix the problem I need to do a reboot but the problem just comes back a few days later. Has anybody seen this problem? It is impossible to get anybody from service on the phone and I'd like to know what the likely issue is before scheduling a service call.