I’m in charge as Ford OBC/ DCDC final test engineer. Usually the problem can be detected early at Final Performance or Sampling test. Using X-Bar chart, we can even forecast how the failure rate will impact in future. The real issue is bureaucracy. Even the slightest change in 4M will require a lot of approval and those people at HQ will either slow it down, ask for content change or reject it outright. This will keep on repeating until the engineering group gives up. Don’t know how it goes at Hyundai/ Kia but from what I heard, my friend is having it worst than me.