'01 Pathfinder Exhaust Mystery

Strange Problem!!



Just replaced the entire cat-back on my truck–When the original rusted out after 100k miles, I had an after market put on, and about 6 months later, the resonator (?) was “swollen and crushed in”-- very very strange.



The mechanic replaced it under warranty no problem, and low and behold it happened again–same type of weird swelling, and a throaty rumble. Decided to go to another mechanic and try a different brand–let’s see what happens now.



Mind you, I had the dealer do lots of work on the engine (mass air flow sensor, injectors, etcetera).



Every mechanic I’ve asked has no idea what the problem can be. I just chalked it up to a crappy aftermarket exhaust.



any thoughts on this mystery!??