As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
RETURNED TO IAD DUE TO PARTIAL ELECTRICAL FAILURE. TERMINAL LUGS L2 (PHASE B) AND L3 (PHASE C) WERE FOUND BROKEN AT LEFT GENERATOR CIRCUIT BREAKER C901. LOSS OF PHASE B AND PHASE C AT L GEN CB CAUSED PARTIAL ELECTRICAL FAILURE. THE WIRE TERMINALS WERE REPLACED.