A wired question: the scale increasing, camera shake disappearing

I'm developping an airplane game. The airplane's Transform is updated in "Update()". The gameObject----airplane cantains many sub-gameobjects, including the plane's instrument panel and a pilot. There is a Camera on root. Camera is updated in "LateUpdate()" with "transform.position = target.position; transform.rotation=target.rotation"; The target is a Transform and I set the pilot's head as the target. Camera looks at the instrument panel.

When the localScale of the airplane is 1, I can see that the panel and the whole plane is shaking frequently and tinily! I tried to update the camera in update and fixedupdate, but none works. Then I change the localScale of the airplane to 20 or larger, the shake disappear. When the localScale is 10 around , the shake slows down. Why? How could I remove the shake when the localScale of airplane is 1?