My left rear window makes a cracking noise whenever I roll it down. If I do it once, it will take a few hors before it does it again. It's been in the shop 7 times for it. The track, weather stripping has been replaced. motor tighten, motor loosen, window out of alignment, these were all the excuses. First time it's been in was at 4700 miles. Now it's at 24500 and still doing it. Has anyone else had this problem? Every dealer I've taken it to says this is the first. Any suggestions?