Dan S is right, that is caused from the hyd controls not being adjusted properly.
Once the arms are near the top, the control should stop the pressure to the cylinder. There is a procedure in the shop manual, too difficult to describe without pictures.
There are also 2 different relief valves. Prior to 168853 uses a 2000 PSI, after uses a 2500.
As long as nothing is leaking, and the hydraulics are adjusted, the crack probably won't get worse unless you do a lot of heavy and bouncing lifting.