As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT NR 6217 - IAD-PVD - UNSCHEDULED LANDING DUE TO CAPTAINS ALT LAGS BEHIND FLIGHT OFFICERS. AIRCRAFT RETURNED TO GATE WITH NO FURTHER INCIDENTS. MAINTENANCE REMOVED AND REPLACED DADC. OPS CHECK OK. AIRCRAFT WAS RELEASED AND APPROVED FOR RETURN TO SERVICE. (M)