Hi Lindetech, thanks for your input. We have 4 separate levers all the same part number, swapping levers around doesn't make a difference to the fault.

Reference wiring fault, without a wiring diagram it's difficult to understand exactly what should be happening with the circuit, but i think the engineer was saying as soon as any lever is pulled, all of the valve solenoids get 48v supply (don't know if thats correct or not), but guess then the solenoids are switched via the return. Will check further tomorrow.