As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING APU OPERATIONS A LOW FREQUENCY VIBRATION ALONG WITH THE SMELL OF BURNT OIL FROM THE APU BLEED AIR. THE MAINTENANCE VENDOR DETERMINED THAT THE APU STARTER/GEN CAUSING THE VIBRATION. THE STARTER/GEN WAS REMOVED (TOTAL TIME IN SERVICE 471.3 HRS) AN OVERHAULED UNIT WAS INSTALLED AFTER THE INSTALLATION OF NEW PAD SEAL.