I don't see why there is so much dispute over this....I deal with warranty claims daily in my business/profession. Yes, you do come across some crazy or unforeseen shit occasionally like this, where something just doesn't seem to add up. But it comes to a point where you "Jessie and MBRP in general" need to take into consideration that the part may have been defected. I've seem numerous "new" parts being delivered to me that don't work out of the box, nothing physically wrong with them that you can see. They just don't work, or they fail quickly.
Instead of playing the finger pointing game with the customer and pissing him off loosing potential business from him and other buyers. Eat the $500-$600, stand by your product and services, recall the damaged product, review and research how it may of happened and take the necessary steps to ensure it doesn't happen again.
If it was an isolated case, then just consider it a manfacturing dud and call it a day. Eating a single axleback system from time to time doesn't sink a company. Pissing off customers and gaining a bad reputation through customer service does.