Why? That is the question and one of the reasons why OEM manufacturers spend a lot of time and money validating designs before they are released.
It could have been undersized for the loads. It could have been a back materials choice. It could have been improperly installed. It could have been the shock loads from the lack of compliance in a heim jointed connection. Only a forensic investigation will be able to say.
They say there are no such thing as a stupid question. They say there is always the exception that proves the rule. Don't be the exception.
