There is 2 likely things that could be causing your sync issues within the jack; either a bad check valve or internal seal.The check valve is located on the bottom of the lowest larger piston as well as a internal seal on the bottom piston. The check valve may intermittently get stuck closed or open and will cause issues or if the seal is bad it will allow oil to pass and the piston to settle. It is a pain and an oily mess to get to either of them as you will have to physically remove both pistons separately from the jack casing to change them. If your going to change the check valves I would recommend changing all the seals, bearing strips, and o-rings along the way just to be safe while you have it apart on both sides.
