I recently had a Zumo 665 installed, now at random times the volume goes down and when I try to adjust the volume instead of just seeing the word "Volume" the display will show "Phone Volume". The bike is a 2010 FLHX Street Glide. I have been looking everywhere I can and don't see anything about the factory radio having a Phone Volume option to turn off or adjust. I did notice that the GPS has an audio jack plugged into a radio antenna. I am thinking of just unplugging that jack as the only use it serves it so that you can hear the GPS directions while listening to the AM/FM radio. But not positive that would even fix this issue. Anyone heard of this before or have an idea how to fix this?