All composited elements in Star Wars weave independently of each other; there are no exceptions.

Subtitles move independently of the background. Starfields move independently of the titles composited on top of them. The sandcrawler matte painting moves independently of the plate it's composited on to. If you stabilize one, you exacerbate the motion of the other. This is because optical compositing required multiple passes through the optical printer, and even the most accurate pin-registered gate cannot maintain absolute alignment. Each pass weaves differently. On an exposure area as small as film, the tiniest movement is obvious. That it worked at all is miraculous, but is also why there are so many edge and fringing errors in composites from that era.

The aggregate motion of multiple items moving independently sort of cancels each other out to a certain degree, and you don't really notice it, but as I said, if you lock one, you suddenly can't miss the other. I stabilize every single shot in the film as I'm working on it, temporarily, and I have yet to see an exception to this rule. And every frame of Star Wars moves around in the gate to one degree or another. There are no stable shots in the film.

Hope that helps.

_Mike