My dad's had this same problem at a year newer. It is a knocking/creaking noise as you drive along. Mostly when you hit a bump or just a patch of road that isnt level. He had it in, and they replaced the seal. I called the dealer and it's still going to be a $115 diagnostic + the cost of labor and part. Dad's was replaced under warranty.

Constant cracking sound from sunroof area. Dealer/service removed glass, cleaned, adjusted and lubed glass.

Update from Jan 3, 2017: 12/07/2016 ~ Sunroof continues to crack. Dealer reports torqued to proper specifications. Continued to get worse.

12/16/2016~ back to dealer with multiple (same) issues: dealer removed sunroof and replaced seals and lubricated tracks as per "star case"