As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT PITCHES UP & DOWN AGGRESSIVELY WHEN ENGAGED DURING CLIMB OUT. HAD TO DISENGAGE IMMEDIATELY & HAND FLY WITH AUTOPILOT OFF. FLT 5370 FOUND THE ELEVATOR SERVO WAS MOVING THE FLIGHT CONTROLS IN THE OPPOSITE DIRECTION FROM WHICH THEY WERE COMMANDED. REPLACED THE ELEVATOR SERVO. PN 622-5027-101, SN ON 1KROH & SN OFF 1NT2R.