Did you ever get this dealt with rdh?
Not sure what you mean when they said the tub twists out of place, but if by that they mean you can see the body/chassis move sideways over the tires when you turn the steering wheel, then your trackbar is either loose, the rod end is worn out, a mount is loose or broken, or the bar itself flexing. Sounds like to me anyway.
You can test the front end components yourself for free though, by having a helper turn the steering wheel back and forth just enough to make the tires move side to side (tires fully on the ground though) while you lay under there and watch what's going on. While having the engine running can make it easier for the helper, it does not have to be on to do this test. Makes for less nervousness when laying under there!
With things moving back and forth, you can see any little movement in steering linkages or flexing in things like the frame or trackbar. Any movement that does not push the next component (excess freeplay in other words) is worn out and not good in most steering components. Rod ends should have no side-to-side movement in them at all. Trackbar bushings will flex a little, but only a VERY LITTLE is acceptable. If you see the bar or it's mounts moving, something needs to be done to eliminate, or at least greatly reduce the play.
When doing this test, you can even see things like cracked frames under a steering box, or loose wheel bearings and ball joints, or even a cracked wheel.
Great tool to get used to using.
However, and I sometimes get heat for this when I mention it, but your description of it starting when you hit a bump sounds like a tire issue to me. Classic symptom, if it's repeatable at the same bump especially. You say it started after the 4" lift, but did you also change tires at the same time? New or used? What size and tread design? Any little curb, pothole, or rock-attacks that you thougt too small to mention? Some tires can be damaged internally by just the right hit. Others just die of old age. Happens all the time. That's why I was asking if you installed older or used tires.
JK's have an issue with trackbar bolts that are too small for the mounting holes, so that if/when they ever work loose, there is a lot of potential play. No matter what the actual problem starts with, any items you have that may be loose or worn can certainly contribute to making a DW more recurring and more vicious.
At the very least, try rotating the tires front to back to eliminate the fronts as an issue. If you've got one dead tire up there, it can sometimes fix the issue. And it's free!
If you've got three or four bad tires though, you're SOL. So to speak...
Good luck. Hopefully you found the issue by now. It's a hairy thing for sure.