As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
EN ROUTE NRT-TPE, THE NR 2 AND NR 3 INS EXPERIENCED OVERHEAT PROBLEMS. THE INS RED WARNING LIGHT WOULD NOT CLEAR. CREW FOLLOWED COCKPIT OPERATING PROCEDURE AND RETURNED TO NRT. REPLACED THE NR 2 AND NR 3 INS COMPUTERS. PERFORMED CHECK AND UNITS TESTED NORMAL.