That Xylem site is pretty neat.
I wonder if you pipe was the new in 1972 class 3 or class 4 high tensile wire that led to lots of failures in the 1980s or if was made out of the older stuff
https://info.xyleminc.com/rs/198-DLL...ODMyOS4wLjAuMA..
It reads like a classic engineering failure study. Take a good working product, reduce design tolerances in areas you think you understand the failure mechanisms, then get bitten by some other not well understood mechanism that was being prevented by the “over design”.