I had the same issue with my cherokeeca few years ago...I never took it in to check it out cause like you it never leaked nor did any seal appear to be damaged. The only thing I could see was that it looked as though the door frame around the window did not make a tight seal around the body of the car almost as if the metal was warped particularly down the windshield pillar.
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2011 Liberty Sport
2 KC Slimlite 130 Watt Long Range on JK Bar
TMS CROSSBAR-CH100 Aluminum Roof Rack Cross Bars
Cobra 75, Firestik Door Jam Mount, HD Spring, 2Ft Firestik