kitchen mixer tap turns off but continues turning back on?

Hi
If I turn our mixer hot tap off it will shut off the supply but then a fraction of a turn further and the flow starts again. I've taken out both the hot and cold valves to compare them. On both, the jumpers and rubber washers are unattached. The washers are held in place by 'push fit' only (but their holes are not small enough to do so) and the jumpers slide freely in and out of their assemblies - is this as it should be? Given that this is the same for both taps, I cannot fathom why the hot only has this problem. Any ideas. please?