As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
JUST AFTER TOP OF DESCENT, AUTOPILOT A AND AUTOTHROTTLES DISENGAGED ON THEIR OWN. AUTOPILOT A WOULD REENGAGE JUST FINE, BUT AUTOTHROTTLES WOULD NOT FOR REMAINDER OF FLIGHT. ACFT GROUNDED. REMOVED & REPLACED AUTOTHROTTLE SERVO MOTOR IAW AMM 22-31-91-000-801, & 22-31-91-400-801. CHECKED GOOD. NO FAULTS NOTED. OPS NORMAL.