Joints not independent

edit

I am trying to set the PID position controller on my 7-DOF robotic arm using ros-control. However, the joints are not behaving independently. For instance when I move joint 2, joint 4 moves a bit as well. This makes the PID tuning complicated. How can I make the joints independent of each other so that I can set each joint's PID separately? Do you think that the problem is because of the inertial values?

Here is a video showing this behavior. I am giving a reference angle (position) to the last joint (the wrist joint). However as can be seen, the joints before are also moving even though I tuned the PID values of each joint. Also, when increasing the damping value, sometimes the link starts vibrating a lot.
https://youtu.be/GnTFysoRYjk

Also, when setting one of the joints (which is on a horizontal plane) as revolute, the link starts moving even when the set position is 0, however when changing it to continuous joint it behaves correctly. Why is this?

Thanks