I have the factory AM/FM 6-disc in-dash CD changer, MP3/WMA playback capability and nine speakers including subwoofer. But I am having two issues with it. 1) At times the volume knob on the radio stops operating. 2) the LCD display goes to symbols and then goes blank. If you power the radio on and off a few times both seem to go away, until the next unsuspecting time it wants to act up. I have been to the dealership and they said the radio has tested OK, so they do not see a problem. Any ideas on what to try myself other than simply replacing it with a aftermarket stereo?