I am not sure what the issue is, however I have a Zre 2010 sedan. I had this problem of noise rattling probably every second when i go on rather not a smooth surface, bumps and corners. Went to dealer three time to check it out, couldn't find the problem. I did some research in other forums, had one guy stated herbs rear seats were not installed properly or bolts are missing. When I suggested to dealer, they had a look at the seats and it's been fixed now. So i would suggest get your rear seats checked as well. Hope this solves the problem