There are quite a few other posts on this, search for them using my name and you can find most. I had this happen on the passenger side, front door. Turned out that the plastic seal that is between the inner door cover and the door itself was bad, which in turn caused the lift motor to actually rust up and quit working. The dealer replaced all of it under warranty. That was about a month ago, and it doesn't appear to be leaking again...yet.