I've had my 2010 4-door Golf since new and had been noticing a mildew odor, but could never find the problem, it would come and go. Finally discovered that the backseat floor behind driver's seat was soaking wet under the mat. It was raining and I could see the water coming in from under the back door, over the plastic "curb" and dripping down under the mat. Took it in for service last week, they said they could not make it leak and they looked under carpet and said it was dry and odor-free (it had dried up by the time I had the appt). Well, it's been raining this week and the floor is soaked again and the car stinks! Going back in next week. Has anyone had this problem?