Those would be two single acting cylinders on that unit. It swings the unit by pumping oil into the rod side of one cylinder while the opposite cylinder is pulled out by the chain. Stopping the swing action would have to be done by the cylinder that is being pulled out. I don't see anything in the parts pages that indicates any component to control oil flow at the cylinders, it all seems to be done by the control valve. There's quit a few components to the swing valve section, your problem is likely in the control valve, just not sure what components would be causing the problem.
Could you possibly follow the hoses from swing cylinders back to the control valve and see if there's any other valves in the swing circuit?