Ross is your best bet as he will know exactly what condition everything was in.
Usually whenever the 'motor specialists' on from the Forum have the motor out and accessible, they lubricate everything, so I wouldn't have thought the bypass valve would be stuck again after Ross has serviced it. Worse scenario is that you may have a corroded hydraulic lead and the pressure is lost. Looking at the motor in the boot, is there still plenty of fluid in the reservoir ?