On some of these rigs, it could be the latch and strike that needs adjustment, because it doesn't pull the door tight enough when it closes. I had to adjust mine when it came home.
If the rattling is coming from the top or bottom edges, some doors needed a little bit of tweaking to tighten them up. You put a 2x4 at the latch area, then lean in on the top and bottom of the door to "flex" it inward a bit. These doors are thin and bend easily. This will help make a tighter seal at the top and bottom.
Lastly, take some silicone spray, and spray all around the rubber door seal, which helps with the squeaks.