As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYSTEM, APU AC GENERATOR DROPPED OFF LINE AT THE GATE DEPARTURE TIME. SWAPPED APU GCU S/N 5295 WITH RT GEN GCU S/N 0815 FOR T/S NO HELP. REINSTALLED GCU'S TO ORIGINAL POSITIONS, PER FIM 24-20-00. REMOVED AND REPLACED APU GENERATOR, OPS CK'D OK IAW AMM 24-21-01.