A couple more suggestions:
a. Open the end cap on each linear module opposite the end with the cable and apply Loctite 243 to the screws that hold down the plastic lead screw retainer. There have been reports of these screws working loose and causing print quality issues. Mine were not very tight from the factory.
b. Use Loctite 242 or 243 on all other screws except the thumb screws and function module mounting screws to make sure everything remains securely assembled.