As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BACKUP GEN SYST EICAS MSG AND BOTH B-U GEN LIGHTS CAME ON IN DESCENT. BACKUP GEN SYST EICAS MSG AND BOTH B-U GEN LIGHTS CAME ON IN DESCENT. NO PARTS SFO. REPLACED BACKUP GENERATOR CONVERTER, SYSTEM RESTORED TO SVC. REPLACED BACKUP CONVERTER M24008 PER LM CALLOUT LM1561. REPLACED BACKUP CONVERTER.