As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT WAS LEVEL AT 3000FT AND CREW NOTICED RED HDG FLAG ON CA'S EFIS AND F/O'S RMI WAS ALSO RED FLAGGED. CREW RAN QRH AND SWITCHED TO THE OTHER EFIS. CREW THEN CONTACTED OPS VIA RADIO AND CONSULTED DISPATCH. FLIGHT RETURNED TO IAH WITH NO FURTHER INCIDENT. REPLACED AHRS COMPUTER IAW SAAB AMM 34-21-05, OPS CHECKED GOOD.