As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE APU WILL NOT SHUTDOWN, CONTINUE RUNNING WITH THE MASTER SWITCH IN OFF. REMOVED AND REPLACED THE CENTRIFUGAL SWITCH ON THE APU IAW AMM 49-60-01. STARTED APU AND SHUT IT DOWN NORMALLY WITH COCKPIT APU SWITCH TWICE. BOTH TIMES APU SPOOLED DOWN APPROXIMATELY 55-60 SECONDS AFTER APU SWITCH SELECTED TO OFF.