As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT GOT A SHEARED BACKUP GENERATOR SHAFT MSG AFTER DEPARTURE. SAMC ADVISED THAT FLIGHT MAY NOT CONTINUE ACROSS ATLANTIC. RETURNED TO IAD. NOT DUMPING FUEL. THERE WERE SEVERAL MAINTENANCE MESSAGES PRIOR TO THE RIGHT BACKUP GENERATOR SHEARED SHAFT MAINTENANCE MESSAGE. THE AIRCRAFT RETURNED TO FIELD. THE RIGHT BACKUP GENERATOR WAS REPLACED. THE UNIT RECEIVED IN UAL SHOP AND FOUND THAT THE SHAFT WAS NOT SHEARED. REQUESTED BOEING TO FOLLOW UP ON THIS OCCURRENCE.