Garage have run diagnostics again and as the actuator wouldn't calibrate the conclusion is either the actuator motor or the clutches inside the transfer box.. not the wheel sensors.
Garage is going to run some tests on the actuator motor, check the oil within the transfer box and then replace the clutch gear within transfer box as a last solution.
If anyone has any other solutions or had a similar issue I would be interested.
Will post back when this is done.