I followed your steps and did not reproduce your problem. A few thoughts:
-When you use track shapes, you can disable points in the shape from being affected. Make sure that this has not occured. Select the Track Points behavior and the Adjust Item tool. Make sure the blue control points have white dots (click them to check).
-Try analyzing with the track points behavior. You do not have to run Analyze Motion to track. You can track from inside any behavior (except unstablize ).
Are there any other steps or detail you can provide that might help us reproduce your issue? Or can you post a copy of the project for someone to try?