As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
PDX - ON FLIGHT NUMBER 2141, RETURNED TO FIELD, HSI HEADING MISMATCH ON BOTH ADVISORY DISPLAYS. THE CAPTAINS SLAVING METER WAS ALL THE WAY LEFT. MAINTENANCE REMOVED AND REPLACED THE NR 1 AHRU AS A PRECAUTIONARY MEASURE. NR 1 AHRU OPERATIONAL CHECK GOOD. AIRCRAFT RETURNED TO SERVICE.