That is the result of the brilliant idea of "concurrent development", where they start producing aircraft for delivery before the testing and validation phase is done. The idea was that computer modeling would obviate the need for extensive real world testing and that the time and cost savings would justify the approach. And of course, another facet of it is that it makes the whole program more difficult to cancel.

The result has been expensive retrofits to the fleet as more and more defects have been found.