Folks,
In my opinion, the M in MD was the undoing of Douglas, the M in MD had had an inordinate and unsatisfactory engineering influence since the takeover of MD by Boeing --- that from old friends who are long time Boeing people ----- even allowing for their bias, I think they are correct.
But, to be fair, long before the above, Boeing made some booboos, I won't try to list them, but just two examples ---- the horizontal stab deficiencies of the 320 series 707, versus the original -300s, and the rudder control package on many. B737.
The ADs are a long read.
Tootle pip!!