As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CTR IRS FAULT LT ON TAXI . SWAPPED RIGHT AND CENTER NAV UNITS TO HELP WITH TROUBLESHOOTING. THE UNIT ON RIGHT POSITION WAS FOUND TO BE NOT WORKING, THE UNIT IN CENTER POSITION WAS WORKING. REPLACED RT IRU. ACP ALL TESTS AFTER THAT, ACFT RESORTED BACK TO CAT 3 STATUS.