As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER GENERATOR 1 FAILED TO RESET ATTEMPTED APU START. AS RPM ACCELERATED THROUGH 50 PERCENT AND APU GENERATOR CAME ONLINE, THE CENTRAL BUS WENT OFFLINE. (FLT 7786) FLASHED LEFT AND RIGHT GENERATOR CONTROL UNIT FIELDS. PARALLELED MAIN, AUXILIARY AND APU GENERATOR CONTROL UNITS.