I to have the 2019 6.2 liter 1500. Just bought it in November of 2018. It has just over 7000 miles on it and I'm having the same problem with the rear window leaking. In my opinion, this really boils down to an engineering and quality control issue.
I've had the dealership "fix" it twice!
Now it's leaking again. Nice truck. Nice power. Not so dry. Hope my sunroof holds up.