I have been having this issue
I have been having this issue on my 2016 Eco Diesel. the dealer tells me they have never heard of this issue at all and when I showed the service manager print outs from RAM forums he told me that those didn't mean anything and that RAM would never let a problem like that go unfixed. It happens about once a week, most times after it has been parked but twice it opened while in a parking lot, I would come out of a store and it would be open. Another time I only noticed it was open as I looked out the mirror and saw my stuff falling out the back. Love my truck, hate the tailgate.