As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING FLIGHT 3134, DUAL HEADING FAILURE INFLIGHT (COMPARATOR) AIR RETURN TO MSP. MAINTENANCE REMOVED AND REPLACED NR 2 FLUX DETECTOR UNIT P/N 622-5812-001 S/N ON 26179, S/N OFF 15446. NR 2 AHRS OP CHECKS GOOD IAW SF 340 MM CHAP 34.15446.