Turned out mine was the rear hatch mechanism also. Dealer had adjusted it twice and also insulated the heck out of the tailgate but was still hearing the noise and it seemed like it was coming from where the tailgate closes and locks into the catch. So I just added some black electrical tape to the catch and now the noise is gone. Wrapped the tape around four times to build it up a little to eliminate play and even if it is still moving on bumps it is no longer metal to metal so cannot be heard.