Alaska MD80, jackscrew
This one was directly a pilot problem.
Why, you may ask, when the stab jackscrew failed?
It completely failed
after the crew attempted many maneuvers, both flaps up and flaps down, to check handling.
Instead of....diverting to LAX or LGB when the problem was first noticed, with minimal configuration changes.
This screwing around with the airplane instead of diverting in quick time defied all common sense logic, thereby contributing directly to the accident.