Stiffness, damping setting in joint drive

As you can see in this picture, I connected this machine with four joints, three revolutejionts and one prismaticjoint. To heft the left arm, I added a linear drive to the prismaticjoint , but no matter which I set in damping and stiffness. It shook and needed a long time to be static, and the two prisms I had added joint between seemed fail to be at the axis I had set in joint Physics, what’s wrong was it?