I know there are a few seasoned techs in here. I swear every time I run, it's all about my frustration with that swing.... Here is the deal, I have realized its nothing really to do with the swing circuit, but a little tunning issue with the brake that sort of lets go a little late and cause a slight jerk. I'm constantly using the machine like a crane so jerky no worky. There is a 'crane mode' switch in the cab, and manual really tells you nothing. I realized years ago it kicked ass! However, I then realized it was a swing brake release and you BETTER know that! She will drift away. All I want is that brake to release a touch sooner and I'm hoping I can find something simple enough to adjust? I don't yet know if the brake circuit is tied into the pilot circuit for swing? Just to make sure it can't move if something is not right? The CLs are not electric over hydraulic so my guess is just a bit sticky. I should mention that under really digging stiff, there is zero issue at all, this is where I am asking that machine to move over 1" and I can 5". I know its a digger but with that brake released, it will do it.
I'm not as familiar with Cat as I am with Deere/Hitachi machines but the swing brake is released on all excavators any time a front function is operated so side loading while digging won't damage the swing brake and the brake shouldn't apply until the upper structure has stopped (the dynamic braking of the swing motor should stop the upper structure before the brake applies.) It could be leakage around the swing brake piston seals, a partially plugged screen in the swing brake pilot plumbing or a stuck/sticking spool in the release valve. It would be best to leave the brake released while you're digging until you get it figured out. Someone with Cat knowledge can probably help you better than I can. Good Luck!