Winters get much much colder in Michigan, so this particular fault would have been uncovered early.

Detroit automakers test their vehicles in places like Arizona and Alaska to account for different climates. I’d imagine Tesla does similar though with fewer test units and models to test some issues are not captured.

I saw a Model S driving in the Chicago suburbs a year or so before the introduction. There was a Roadster owner in my town and I wonder if he was offered the chance to do long-term testing in the weather here.