As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURN TO FIELD DUE TO NR 1 ENGINE OIL TEMP. INDICATED OVER TEMP. THE TUBE-TO-BOSS ADAPTER, WHICH SECURES THE 12TH STAGE AIR COOLING LINE FROM THE NR 3 BEARING BUFFER AIR COOLER WAS FOUND CRACKED. THIS FAILURE RESULTED IN LOSS OF 12TH STAGE COOLING AIR FROM THE BUFFER AIR COOLER TO THE NO. 3 BEARING COMPARTMENT. THIS IS A "FIRST-OF-KIND" FAILURE.