Rear Window tapping noise
 

I have a 2012 Mazda3 iTouring and there is a tapping noise coming from the rear windshield area. I took it to the dealership and they told me that it was plastic spacers that they use on the window. When I told them that it does it when it is cold and not so much when it is warm outside they said it was because the plastic pieces shrink. They removed the pieces but guess what it still does it. I called the dealership and they said to bring it back in and the mechanic would go for a ride with me. Well of course it had warmed up by the time I left work and brought it there it wasn't doing it but I hear it randomly all the time and it drives me crazy. Angry that I paid for something to be fixed and it hasn't been fixed. So frustrated! Does anyone have any experience with this? I would love to get some input on this.