Folks, I would not set and leave any less than one valve fully open! If one is closed then you need to be aware of the sound of the pump and when you hear it laboring release the switch. If you expect to have all slides functioning then all valves should be left fully open. The issue is building up excessive hydraulic pressure when hitting end stops and not having another hydraulic cylinder to move freely... Likely you exceeded the seal pressure if operating the motor beyond full extension expecting the slide that has the valve partially shut to move. You can expect premature pump failure and blowing fitting seals as hydraulics is all about building pressure and moving pistons. When things stop moving, stay alert to motor noise, and release when it begins to labor...keeping an eye on your slide position that it is fully extended.