I think it has a lot to do with driving with the top up and the windows down. There is too much wind buffering on that rear window for that. I have a few friends with other rag tops - all the ones with back window issues are the ones that drive around with the windows down. My car has 2 modes - top up, windows up or top down, windows down. The bad news is that once it starts to go it seems to just be a matter of time. I don't think it has anything to do with who made our car, its just part of having a rag top with a glass rear window.