The camstack rotates any time the machine is running. When the stitch selectors are in straight stitch mode (A-K), the cam followers are pulled away from the camstack so they do not move the needlebar left or right.
That's the good news - now for the bad. You should not hear a noise from the camstack. You don't say what kind of noise (squeak, grinding, clicking...) so it's kinda hard to diagnose from a distance. There is a gear below the camstack that benefits from grease but to get to it you have to remove the camstack and then you have camstack timing issues to deal with.
Ed