Squealing PRV - Any ideas?

Over the last few weeks, our Watts N35B PRV has begun to "squeal" loudly any time significant water is running (washing machine, shower, etc.). I have tried varying the water pressure, and removing and cleaning the screen (just to see if there was any blockage - nothing). I did not remove the interals.

Anyone have an idea of what to do next? Our home is about 9 years old.

Thanks

Peplacement?