As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FOR FLIGHT 4573 DURING THE PRE FLIGHT INSPECTION FOUND THE GUARD FOR APU FIRE EXTIN BUTTON HAS BROKEN SPRING. THE AIRCRAFT WAS REMOVED FROM SERVICE. REMOVED AND REPLACED THE APU FIRE SW GUARD IAW AMM 20-13-04. THE AIRCRAFT WAS RETURNED TO SERVICE.