Yeah, I can imagine the feeling in the steering wheel they way you’ve described it, and I certainly understand your obsession with the problem.
You’ve suspected traction control in your posts, which might point to a bad sensor - maybe a yaw sensor or accelerometer. But it seems to do it with TC turned off. And the TC doesn’t seem to relate to any of the work you had done. Since it showed up right after that work, seems like there must be a connection, which is what leads me to the rear suspension.
Wondering if it changes if you have the EAS pumped up to off road height (or lowered to access mode)? Or maybe putting some weight in one rear corner or the other? Just trying to think of easy things that might give you a clue on the suspension side.
Also, does the ARB air locker run off the EAS pump, or did they mount another pump someplace? Just wondering where else they might have been working on the car.
Aside from that, and just reading back through your posts, I’d start going through your front end more thoroughly if you haven’t already. I know you said the dealer looked at it, and they did an alignment, but did they really go under there and test for any slack in the u-joints, cv joints, ball joints, front control arms, etc. I don’t trust dealer’s work anymore. I find them to be lazy in diagnosing things.