As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 431 SHV/LAS - FLIGHT CREW REPORTED THAT DURING CRUISE, HEADING FAIL ON BOTH FMS'S. 30 DEGREE SPLIT BETWEEN F/O'S NAV DISPLAY AND RMI, QRH 31.2 PROCEDURE APPLIED. LAS VEGAS MAINTENANCE REPORT THAT THEY REMOVED AND REPLACED THE NR 2 DIRECTIONAL GYRO. A SATISFACTORY OPERATIONAL CHECK WAS ACCOMPLISHED PER AMM 34-21-09. THE AIRPLANE HAS RETURNED TO SERVICE.