As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
GEAR NOT DOWN EICAS WITH CONFIG ANNUNCIATOR ON. HORN GOING OFF. FOUND NO FAULTS IN PSU. PERFORMED FIM 31-51 FAULT TREE 817. SEEMS TO STAY IN LANDING GEAR CONFIG TEST MODE ALL THE TIME. ISOLATE LDG SWITCH ON PANEL M10398. WORKED FINE. TRIED CLEANING SWITCH WITH CONTACT CLEANER. WORKED GOOD FOR ABOUT 10 MINUTES BUT FAILED AGAIN AFTER SEVERAL TESTS. PLACED ON ORDER M10398.