Brother, you're not alone. But be it known, the problem is imho a design issue. There are 16 holes in the roof under that rear spoiler. In addition, the rear window encasement is prone to cracking, something in the design has too much flex, recall those torsional rigidity commercials Chevrolet used to tout. Torsional rigidity requires an engineer and apparently focus groups are designing vehicles these days and not engineers. Everyone's truck is 100% susceptible to this leakage. Driving rain and car wash probably OK. Sitting outside in the rain for days, or covered in snow, you're gonna leak and it's going to ruin the vehicle.