I have a Beocenter 7007 with a distortion problem in the left channel when playing records. Sometimes it is fine other times it is there. If I press stop to make the arm lift and then phono to lower the arm again the distortion often disappears. The next day, however it comes back and I have to go through this process again to clear it. Does anyone know what the fault may be? The stylus is clean abs the cartridge pins are clean and making good contact. Any help would be appreciated.