We installed a cut off valve for both cylinders between the valve and cylinder. Tilt the mast back then close the shut off so no fluid could go back to the valve. This isolates the cylinders so if the mast still moves forward the cylinders are bad. Since the mast did not move forward we assumed the valve was bad as there is no electrical voltage at the valve solenoid when the control handle is released. Unfortunately for us this did not fix the problem. Thanks.

When you isolated the cylinders from the valve were they still hooked together hydraulically or were they isolated independent of each other?