A Pillar Leak
 

Trying to troubleshoot a long-time leak on the passenger side A-pillar on a 2013 F150 Lariat. The leak occurs after a period of rain but does not show up after washing. The drip comes from the top screw holding the grab handle. Taking the handle and molding off after a rain shows very little moisture inside. (see pics). I've checked and cleared the sunroof drain tube several times. Opening the sunroof after heavy rain shows no water accumulating around the opening. There is no sign of moisture or staining around the GPS receiver.

Does anyone have experience with this? All suggestions will be appreciated.
https://cimg8.ibsrv.net/gimg/www.f15...53ed4354de.jpg
https://cimg9.ibsrv.net/gimg/www.f15...db6d91f2b9.jpg
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