Maybe I was lucky, or maybe I had a super-excellent operation, but when I was making over 100 different products a year and quantities on an individual product ranging from 100 to 1,000,000 pieces per year, I can't recall a year when we had more than 5 CAR investigations, regardless of whether the suspected nonconformance was by supplier or us and whether we initiated the investigation or the request was generated by a customer. Even then, likely as not, the nonconformance was not really a product nonconformance, but a misunderstanding of the specific requirements which should have been handled in the Contract Review process.
The sole difference may have been that EVERYONE in our organization took a CAR as a personal affront and we moved heaven and earth to resolve it as a team and never, ever, pointed a finger of blame. We treated each CAR as either an opportunity for us to learn or for us to educate (our staff, our suppliers, our customers.)