As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING CRUISE FLIGHT THAT THE AHRS NR 1 & NR 2 DISAGREED & KICKED THE AUTO PILOT OFF. TROUBLESHOOTING FOUND THE AHRS UNIT PN 622-9336-400 SN 1VYVB DEFECTIVE. THIS UNIT WAS AN OVERHAULED UNIT THAT WAS INSTALLED 17 HRS TT PRIOR TO THIS FAILURE. SN 1VYVB WAS REMOVED FROM SERVICE & AN OVERHAULED EXCHANGE UNIT WAS INSTALLED.