As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - LT MAIN TANK NR 4, TANK UNIT LO-Z TO SHIELD READING LOW. REPLACED LT MAIN TANK NR 4 TANK UNIT IAW AMM28-41-01, FAILED RES CK BAD FROM STOCK S345T002-133, SN K0333. REPLACED LT MAIN TANK NR 4 TANK UNIT IAW AMM28-41-01.