As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
OPERATIONAL CHECK OF EMERGENCY POWER SUPPLY UNITS BY BITE-CHECK FAILED FOR 12WL. / REMOVED AND REINSTALLED EPSU (12WL) IAW AMM 33-51-38-000-001-A AND 33-51-38-400-001-A. OPS CHECKED GOOD AT THIS TIME.DURING TROUBLESHOOTING OF EPSU (12WL) CLEANED CONNECTOR AND REINSTALLED AND FAILURE INDICATION WAS CLEARED."