As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - AIR TURN BACK DUE TO UNRELIABLE LT MAIN FUEL TANK QTY. IMBALANCE WOULD GO TO 2400 LBS BETWEEN RT & LT MAINS W/I 30 SECONDS. R & R LT DFU IAW AMM 28-41-03. R & R LT DEFUELING VALVE BODY IAW MM 28-26-01. R & R LT DEFUEL VALVE ACTUATOR IAW AMM 28-26-11.