Either bad internal seals or check valves can cause the same problems. You have to remove the pistons to get to both the internal seals and check valves so I would just change them all while you have it apart. Also when finished make sure you bleed each jack head out individually.

Also another more obvious issue could be that the jacks are out of plumb and binding on the platinum plate. This can cause the jack not to do a proper re-sync.