Add me to the list, mine does it also... New 2013, about 2 months old (actually born 4/13) and has done it from day 1. Sucks because it sounds and looks cheap but whatever, the windows still work.
I'll add it to my list of things to get checked out when I take it in for its first oil change along with the bubbles in the paint, ticking engine under light load, smell during hard acceleration, drivers side A pillar squeak and display screen in the gauge cluster randomly staying on after the truck is off.... Just a few issues LOL. The quality control on this SUV is almost comical.
Love the Explorer but holy crap never seen this many issues in a new vehicle...