The Jerky issue is if you try to move the 3pt lift up smoothly slowly, it will not do so. At least mine wont, you can move the lift down, slowly and smoothly all you want, to "feather" the position, but you cannot move it up slowly to get to a particular position, it will be a sequence of "jerks". If you move the control in one rapid/moderate up, motion of your hand it will just jerk once at the end of the 3 point travel motion. What I do is just raise it up past where I want it to be, then "feather" it down to the exact position where I want it. I hope this makes some sense. it is kinda hard to describe this, but easy to see in action. If you lower the hydraulic pressure/flow rate (?) to the 3pt, by operating the lift of the front end loader at the same time as you try to raise the 3pt, the problem is solved it will raise smoothly and slowly without jerking.
James K0UA