I have this arrangement under my sink and my washing and machine and dishwasher are connected into those appliance valves.

I was replacing my dishwasher today and tried isolating at the appliance valve but it was still letting a ready trickle of water through. I then had to isolate with the lever valve for all cold water.
Can this valve be fixed or does it need replacing? If this is an issue, is it a common fault with this type of fitting?

I was replacing my dishwasher today and tried isolating at the appliance valve but it was still letting a ready trickle of water through. I then had to isolate with the lever valve for all cold water.
Can this valve be fixed or does it need replacing? If this is an issue, is it a common fault with this type of fitting?
