Water pressure regulator ticking ?

Water pressure reducing valve ticking ?

Hi - my water pressure reducing valve has started to make a knocking or ticking sound. It's not doing it all the time - but when it does it's very annoying, as it's right below our bedroom !
The noise only occurs when there is no water running. If I turn on a tap it goes away.
Is the solution to rebuild or replace this unit ?
Thanks - Brendan.

If you can find a rebuild kit.

Most of the time, we replace the entire prv

Thanks for the reply. Have you come across this problem before, is it common ?