In the early 70s, DC-10 planes had disastrous failures with cargo doors. It proved how massive a havoc faulty cargo doors can have on the planes. Despite those two incidents with Boeing 747 planes in the 80s prove that Boeing were not careful enough to avoid problem with the cargo doors. In fact, there is a striking similarity with what happened to DC planes in 1972(a warning) and in 1974(not learned from the warning) and what happened to Boeing 747 in 1985(warning) and in 1987(not learned from warning).
Why didn't Boeing learn from what happened to DC-10 planes?