I dont know what clamp this is but most manufacturers install lock valves inside the cylinders just incase the packing or the valve is leaking internally after the clamp is shut closed the valves hold the cylinders so not to drop the rolls and kill someone l know if it is cascade clamp the valve are set at around 900 psi to open on the back stroke it is possible that the valves in one is going bad just thinking but you will have to take pressure test to see were the problem is