Recurring Pinhole Leaks
High mineral counts can be a problem, not having proper dielectric unions and my opinion CHEAP pipe. I have seen cheap pipe have 50 pinholes where the rest of the house was fine the funny thing we could still see the stamps on the pipes and it was the cheap brand that had all the leaks. Replaced those sections and 10 years later the rest of the pipes are still fine, just the thinner cheap copper was the problem.