I had this issue, as well as the doors being hard to open at times. While we were in Yellowstone last week I decided to see what was going on with them. It turns out, the screws for the wheels were very loose on mine, and not adjusted well at all, I snugged them up, and locked the door closed during travel. They work smoothly, and there is no vibration on the road... Not to find all the other rattling items!
2012 Jayco Greyhawk 31FK