As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 640 - DTW - AUTOPILOT VIOLENTLY PITCHES UP AND DOWN DURING CRUISE FLIGHT. AUTOPILOT CONTINUED TO AUTOMATICALLY DISCONNECT. BOTH PILOTS HAD TO OVERRIDE THE AUTOPILOT TO MAINTAIN ALTITUDE AND CONTROL. TRANSFERRED TO DMI NR 00151 MEL 22-1 CATEGORY 'C'. (M)