As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TRAILING EDGE FLAP LIGHT CAME ON WHEN MOVING FLAP HANDLE FROM 20 TO 25 DEGREES FLAP POSITION. FLAP INDICATOR REMAINED AT 20 DEGREES. A/C LANDED SFO UNDER AMBER ALERT. *S/D* THE CAUSE OF THIS DISCREPANCY WAS NOT FOUND. TROUBLESHOOTING AND OPERATIONAL CHECKS WERE ACCOMPLISHED PER APPLICABLE MMS AND NO DISCREPANCIES WERE NOTED.