I have the same noise - it's just a poor design for the rear seat recliners with no way to fix it that I can see. Frustrating, because there are so many other things I'd rather have had than reclining rear seats, which will literally never be used. Lights in the cargo area, a rear wiper that makes a full arc, etc - things that were dropped in the 5th gen but that would get used and appreciated quite a bit more than reclining rear seats, and probably cost less to include.
It would be interesting to do a survey to see how many people have used the reclining rear seat function - my guess is a lot of folks probably don't even know its there.