As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FIVE SECONDS AFTER LIFT OFF, EICAS MESSAGE APPEARED: ELEC AC BUS - NR 1 AC BUS BECAME ISOLATED AND UNPOWERED. WOULD NOT RESET PER NNL ELEC AC BUS CHECKLIST. FOUND NR 1 GCU DIFFERENTIAL LOCK OUT. REPLACED NR 1 GCU WITH KLM LOAN PART. CARRIED OUT CMC GROUND TEST & OPS CHECK ON ENG RUN. ALL SATISFACTORY.