I have no experience with this...with Cadillac.
But with other cars when I have had problems with a dealership service department, I would try once or twice to work it up through their management.
If I got no satisfaction, and I have had that happen with Nissan, I would just go to another dealership and we would get agreement up front that the issue was under warranty and needed to be repaired. If we agreed on this, then I would have them do the job.
There is no reason your window should "thunk" or bottom out, now or even when the car is old.
But as Koz says, you can get hold of Customer Assistance.
Here is their web site.
http://www.cadillac.com/cadillacjsp/...contact_us.jsp
Note that you have a couple of items that might particularly interest you.
You can report a problem you are having
you can find the answer to a vehicle related question.
OR you can call them.
Have the following info ready:
Your name, address, and home and daytime telephone numbers
Your Vehicle Identification Number (VIN), which can be found on your registration
Dealership name and location
Vehicle delivery date and current mileage
Nature of your concern
1-800-333-4223