Took the master bedroom apart yesterday to track down the leak:
I was assuming it was emanating from the front exterior seam (red arrows below)
And it was. This is on my back looking up. Looks like the seam is not sealed on the exterior from the factory. When driving, the wind pressure flexed the joint and the rain got in (I used a power washer to simulate the rain
Now the question; should I use butyl rope/caulk or Dicor caulk on the exterior?