As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT HIGH PITCH ATTITUDES, UNWANTED FUEL TRANSFER OCCURRED FROM THE LEFT TANK TO THE CENTER TANK. THE AIRCRAFT CONTINUED TO IAD. FILLED LEFT AND RIGHT MAIN TANKS TO FULL CAPACITY AND PRESSURIZED TANKS USING THE FUEL PUMPS. TAXIED AIRCRAFT AND VERIFIED NO FUEL TRANSFER. REPLACED MOTIVE FLOW SCREENS.