As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FUEL IMBALANCE IN FLIGHT OF 1900LBS WITH FUEL CONFIG MESSAGE. 7.2 LBS LEFT TANK, 9.1 LBS RIGHT TANK. ALL ENGINE INSTRUMENTS NORMAL INCLUDING FUEL FLOW. FMC CALCULATED AND TOTALIZER FUEL WITHIN 100 LBS NO FUEL IMBALANCE NOTED DURING ENGINE RUNS. REMOVED AND REPLACED BOTH CENTER TANK MANIFOLD DRAIN CHECK VALVES IAW AMM 28-21-05-401. REMOVED AND REPLACED BOTH FWD AND AFT CROSSFEED VALVE BODIES IAW AMM 28-22-02-401 UP TO STEP F (14).