As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT WAS NOT GROUNDED: BRIEFLY LOST POWER DURING SWAP TO JET BRIDGE POWER FROM APU. DOOR 2L/R EMERGENCY EXIT LIGHTS AND CENTER EMERGENCY EXIT LIGHTS BETWEEN AFT LABS DID NOT ILLUMINATE DURING THE POWER OUTAGE. MAINTENANCE REPLACED AFT EPSU BATTERY IAW AMM 33-51-38.