Happijac failed while driving down the interstate!

I agree with the tech: the roll pin failing while driving (under almost no stress) is highly unusual. Perhaps abuse by previous owner causing a latent crack?

However in the circumstances I disagree with the tech: I would replace the other three. It is pretty easy to do, doesn't cost much, and there is at least a possibility that whatever history led to the failed one was also visited on the other three.