i have taken my cylinders apart. they are two stage. so it has a total of 4 pistons, each one has a forum of the same problem. the set of seals that are on the threaded end ( the side which the rams thread into) are tighter. i cant really just pinch them out of there groove like i can the other set. i would assume this is from over locking? or just going up fast and the heads stopping hard on the cylinder?