As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5756, IAH TO SDF - DURING CRUISE, THE CREW RECEIVED AN APU HIGH OIL TEMPERATURE MESSAGE ON EICAS. THE FLIGHT DIVERTED TO LIT AND LANDED WITHOUT INCIDENT. MAINTENANCE INSPECTED THE APU AND VERIFIED THE OIL WAS SERVICED TO THE CORRECT LEVEL. THE CONNECTOR TO THE HIGH OIL TEMPERATURE BULB WAS CLEANED AND RESECURED. THE APU WAS RUN WITHOUT FURTHER DEFECTS. ON THE 31ST,THE OIL COOLER WAS REPLACED DUE TO INTERNAL CLOGGING AND LEAKAGE.