The same problem has been found on several plans. Far too many and too high a percent to not be a systemic issue. A phone call or shift change might explain one or two errors, not the same error in many planes across multiple airlines.
They don’t build 100 of those things a day. They don’t even average one a day. Whatever the issue, it went on over quite a period of time.
Given the other issues with the 737 Max line, it is reasonable to believe there would be a good chance of improvement if regulators were more heavily involved.