So I had this exact same issue on my 2020 Ranger. After a year 3 dealerships, (6 of that the truck sat at the last one waiting on parts) two rear windows, door seals, AC accumulator housing replacement they still couldn't fix it. They literally stripped the interior out three times. They'd say it was fixed, only to have it return a couple weeks later. I had also spent hours with a water hose, systematically running water on section after section waiting between each one desperate to find...
Musty/mold smell after carwash/rain
Musty/mold smell after carwash/rain