As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
INSPECTION TYPE:N/A ATB - L NAV WOULD NOT ENGAGE - WHEN PRESSING L NAV SYSTEM LIGHTS ON PANEL WOULD SHORT OUT. V NAV WOULD NOT ENGAGE. FLT LEVEL CHANGE WOULD NOT ENGAGE. DEFERRED PER MEL 22-11-4-11. M402419 ASSIGNED. ***SDR FILED OPEN***