keesje.
Very infrequently, though more times than acceptable, this type aircraft experiences rare circumstances, generally weather oriented, that cause it to drop out of autoflight (autopilot). In these circumstances, the pilot(s) are required to fly "manually", a more and more infrequent concept. The results can be loss of control, uncommanded excursions of flight path, and other disconcerting and unnecessary events.
Necessary competence on such occasions has been found wanting, and incidents and accidents have resulted. The maker of the aircraft, and the pilots, both have work to do.
And the regulators.