43,000 miles on my 2020 3500 HD Silverado, I found water leaking in the rear window at the top of the frame. I called the dealer they said they would have to remove the headlines but suspected it was a bad seal they might have to replace the window. I took it to a. Auto glass replacement company I trust the technician said it is most likely leaking around the bolts that hold on the 3rd brake light assembly. He said a friend has a 2019 Silverado under warrantee the dealer removed the headliner and sealed the bolts that hold the 3rd brake light. I also saw a U Tube video on how to remove the headliner and reseal the bolts.
Has anyone else had this problem please let me know.