Hi Meagain,
It might be an aged/dirty pot and needs cleaning; you could try a cleaner spray like Caig Labs produce. I've used the latter on a 40-year old Sony portable radio (with an excellent AM/FM tuner section) to keep the volume control quiet and operating. When it oxidizes, the control becomes intermittent and noisy. If I spray it once a year and move the control rapidly back and forth after spraying, it's fine for another year or so.
It also might be a cold solder joint on the back of the control where it connects to a circuit board. If you have a technician check it, he should be able to spot the fault.
Good luck.
