If it's only one bracket that's doing it, then I would replace that bracket or take it off, straighten it, and weld the corners to give them more strength. The cotter pin solution also sounds reasonable. It being faulty because it came from a big box store sounds like a desperate conspiracy theory. I beat the crap out of my Raptor 60" and have never had to replace those brackets. I've broken the threaded rods the deck hangs from, but those brackets are holding firm.