How long have you had the bag for? If not for too long, wherever you bought it from should defintely replace it for you or sent in for repair.
When I first bought a Muse from NM, I returned it a week later because the stitiching in the back was coming off. They gave me a new one and informed me that it if happens again, just bring it back and they'll send it in to the manufacturer for repair. It helps to have a good repoir with your SA.