As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING HEAVY CHECK EPSU TEST FOUND AFT EPSU (13WL) FAULTING FOR INTERIOR AND EXTERIOR LIGHTS. AIRCRAFT WAS GROUNDED. REMOVED AND REPLACED R4 DOOR SLIDE IAW AMM 25-62-44-400-803-A. OPS TEST GOOD. RE-TESTED EPSU BATTERY TEST IAW AMM 33-51-38-400-002-A. OPS TEST GOOD. NO FURTHER FAULTS DETECTED. AIRCRAFT WAS RETURNED TO SERVICE.