As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS GROUNDED: PILOT REPORTS DURING DESCENT LNAV AND VNAV DISCONNECTED SEVERAL TIMES AND WOULD NOT REMAIN ENGAGED .AUTO PILOT B WAS ENGAGED ON PATH AND COUSE. MAINTENANCE PERFORMED LAND VERIFY TEST IAW AMM 22-11-00. FAILED ON ELEV SERVO AMP FCC-A. REPLACED FCC-A IAW AMM 22-11-33. ALL OPS TEST PASSED.