[MagicRat]

If the bolt that came with the joint failed, it may be counterfiet. Fake bolts made overseas have been a big problem for industry over the past 25 years.

They are fake simply because they are not made to the specifications indicated on the bolt head. China, where many auto parts are made these days) is awash in such fasteners.

IMO if you still have the failed parts, call NHTSA and Public Citizen, to let the authorities know of this problem, and Autozone head office to get some compensation. If this is a one-time-only situation, nothing may happen, but if your experience is corroborated by other complaints, something may come of it.