As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EXPERIENCED AN UN-COMMANDED 400 DECENT BY THE AUTOPILOT. PILOTS ADI TUMBLED 15 DEGREES WITH HEADING & NAV MODE UNRESPONSIVE. CREW DESCENDED ACFT TO FL020. CONTINUED FLIGHT WITHOUT AUTOPILOT TO HOME BASE. R & R THE AUTOPILOT AMPLIFIER PN 522-2900-028 SN 2617. R & R NR 1 VERTICAL GYRO WITH PN 7000622-901 SN 94067506. WORK PERFORMED IAW MM 22-10-04 & 34-20-07. SYS OPERATIONS CHECKED.