I would check the rubber grommet at the top of the liftgate. This is where the wiring harness for the wiper motor and electric de-fogger pass through the deck. Sometimes this gets unseated when drying or wiping that area. Worth a look.
And your warranty covers the car "bumer to bumper" for 3 yrs or 36k. With the exception of "wear" items, re: wiper blades, clutch disk, and brakes.
Hope this helps.
"The present day composer refuses to die"
Edgar Varese 1883-1967