As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SJU T1218/21 EN ROUTE SJU-JFK GOT AC BUS ONE OFF LIGHT ON OVERHEAD ELECTRICAL PANEL AND LOSS OF ASSOCIATED AIRCRAFT ELECTRICAL SYSTEMS. RETURNED SJU AND LANDED WITHOUT INCIDENT. REPLACED CIRCUIT BREAKER 5XN FOR NORMAL BUS ONE SUPPLY. SYSTEM GROUND CHECKED NORMAL OPERATION.