The key to identifying a problem is not the “what” it is the “why”. The “why” sadly is the broken corporate culture at Boeing. 20 years of prioritizing short term profit over engineering and production excellence is at the root of this problem, just like virtually every other Boeing failure.
The shim issue wasn’t caught until many flawed aircraft were produced because Boeing successfully argued with the FAA that a computerized QA process could replace the work of 220 QA personnel. This move was wholly designed to reduce costs and appeared to be implemented without, and boy does this sound familiar; a full risk analysis and over the objections of mid level management.
Another triumph of clueless MBA bean counters in the C Suite being penny wise and pound foolish. Sadly I think the rot is so deeply entrenched in the DNA of Boeing that it is too late to fix the company as it is currently organized.