When you took the calls inside and ran them, how long were they inside before you ran them? If you run a glass surface in freezing cold temps they will hair line crack because the glass can't handle that cold of weather, the vibrating of the surface cracks them. As the calls warmed up they flexed and swelled and that broke the glass all the way through. If you ever do that again, place the calls in your refridgerater, that warms them up slowly because your fridge is warmer, then take them out the next day and let them finish warming up in the house away from the heat. That will help keep them from flexing or swelling up. Us northern boys have to deal with that a lot, we hunt in the late fall seasons at -15/-25 and keep our calls in a pocket with a hand warmer.