I have a335 Minnie Moline, with a loader on it, The loader will pick up large round bales fine, and I can find no external oil leaks. when I hit the control lever, in the up direction, the loader will drop 5 to 6 inches, before it starts going up. I took the 2 spool control valve off, and took it to a hydraulic repair shop, and paid to have it rebuilt. After reinstalling the control valve, the thing is still the same. I changed the oil in the unit, and didn't find any water in the oil, and it wasn't foamy , like it had air in it. I refilled the loader with hydraulic fluid, ran it up and down, to remove air, and still have that small drop when I move the lever to up position. Is this a cylinder seal problem???