By Customer Service, do you mean a certified Xerox technician?
Normally a Xerox tech would short the door sensor and run the printer with the doors open and possibly a stethoscope to find the noise and replace the part making it. Was this what was done?
We have a WC7545 and it's making a very loud clicking noise when something is printed. Seems to be at the very end when the paper is released. We've had customer service here more than once, the rollers have been changed, there is no paper caught, yet still this noise is occuring. Not sure what to do next?