My RNS50 intermittently plays sound only on one of the two speakers. Sometimes the sound switches to the left side, sometimes to the right within seconds. Often when I then increase the volume, the audio goes back to coming from both speakers again. I am not sure whether it is fully switching sides, or one side just becomes much quieter than the other side. The fading left and right is not a clean digital change, it sounds more analog accompanied by a scratching noise sometimes. Does anyone have an idea what this could be?