Y Plan - Mid Position Valve 'fault'?

Hi, I have BGMVSP-23 'mid position' valve.

(I believe a Y plan setup)

Basically the pump only runs when the cylinder calls for it.

The valve appear to do all the right things, i.e.:

CH H
HW W
CH&HW M

So 2 issues:
1. It's just that when only the CH is on, the pump doesn't run / boiler doesn't fire
2. IF both are on, initially everything fine (valve in M position, rads hot), however once the cylinder is up to temp, the pump switches off - so you end up with a cold house, even when the CH is set to continuous on the programmer and the Room stat is asking.

As I understand it, there are two switch wires - white & grey, and if either is live they should make the orange live to run the pump?

So is it the programmer faulty.

Or the microswitch in the actuator

Thanks for any help.