As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FUEL IMBALANCE LT AND RT MAIN TANK QUANTITIES DIFFER BY A PRE-DETERMINED AMOUNT. 3700 LB IMBALANCE. BALANCED FUEL BY CHECKLIST. ALL SYS NORMAL. CREW REPORTED THE IMBALANCE OCCURRED AFTER THE FUEL WAS USED FROM THE CENTER TANK. THE RT WING WAS LOWER THAN LEFT BY 3700 LBS. CREW ACCOMPLISHED BALANCE PROCEDURE AND REMAINED BALANCED SINCE. REPLACED FQPU PER AMM, OPS CHECKED OKAY.