Why does the cylinder retract a stroke after reaching the position? How to adjust the speed of the cylinder? How to choose the stroke of the cylinder?

The quality problem of the cylinder itself can be replaced. I've been in this situation. When * * * uses the same origin, it is most obvious when there are two cylinders acting at the same time. At first, I thought the pressure of the air source was not enough, but it would still retract after the pressure was adjusted to be stable. Initially, it was estimated that the cylinder itself was leaking and the piston sealing ring inside was leaking.