This happened to me twice last year. First time was the first game I wore them at, failed at half time. I emailed both Smitty and the company I ordered them from and the overnighted me a replacement pair. Wore that pair twice, and on the second game, it's zipper too failed. They sent me a third pair. It was OK and never failed. I spent about $14 each to repair the two bad zippers.
My R said I had to stop looking at the cheerleaders.
Smitty has awesome customer service.