As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UPON VISUAL INSPECTION OF THE POWER TURBINE SECTION WHEN REMOVED FOR 10W POWER REPAIR. DISASSEMBLED P.T. ROTOR AND FOUND CRACKED DIAPHRAGM THROUGH NR 4 NOZZLE INNER BAND. POSSIBLE CAUSE IS DUE TO NOZZLE UNABLE TO HANDLE STRESS FROM HEAT. NOTE: THIS DIAPHRAGM HAS BEEN UPGRADED PER ALLISION BOOK FAX 97-AMC-051 TO PREVENT THIS PROBLEM, BUT IT CONTINUES TO OCCUR. CONDITION OF PART IS REPAIRABLE.