As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FIRE EXTINUISHER DISCHARGE SYSTEM TUBE ASSY WAS FOUND WORN DUE TO VIBRATING CONTACT WITH THE APU PNEUMATIC DUCT LOCATED IN THE LEFT SIDEWALL OF THE C-2 B/B AT FS 1351 TO FS 1439. THE (P/N 453T2620-100) TUBE ASSY WAS REPLACED REF DWG 453T2620.