As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AUTOPILOT DID AN UNCOMMANDED 3000 FT MIN DESCENT WITH PITCH WHEEL IN ALTITUDE DETENT. FLIGHT 158, STA ALB. COULD NOT DUPLICATE. SUSPECT PITCH COMPUTER INSTALLED FOR TRIM PROBLEM CAUSING DIFFICULTIES WITH ALT HOLD. REMOVED AND REPLACED PITCH AXIS COMPUTER. SYSTEM OPS CHECKED GOOD IAW DC-9 AMM 22-10-00-5.