Shirl writes:

There are PLENTY of carefully maintained aircraft that have problems and
failures, some resulting in accidents and some not. The concept you
aren't understanding is that mechanical failure is not necessarily an
indication of poor/careless/inadequate maintenance, and in fact, more
frequently than you believe, things go wrong even on airplanes that are
vigilantly maintained. Bottom line, even though you and your mechanic do
everything humanly possible, there is simply no way to assure an
aircraft isn't going to have a problem.

Then it must be a defect in design.