just got a second hand 5t log splitter. Ran it for approx 15 mins with the bleed screw closed. The ram will not retract back to its starting position. it stays about half way. It will still run forwards but not back. I have filled up the oil and tried running it with no log with the bleed screw open but it still wont go back even if you try pushing it. Also tried realigning the valves as the pic below but that didn't help. I think it can either be oil which isn't being drained or the spring which is isn't working. Any ideas?