As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
TRIP NR 1133786, CREW REPORTED SMELL OF BURNING RUBBER OR OIL IN THE CABIN WITH THE APU RUNNING. SMELL WENT AWAY 2.5 HRS INTO THE FLIGHT AND CAME BACK WHEN THE APU WAS STARTED. THE SMELL INCREASED WHEN THE PACKS WERE TRANSITIONED FROM THE ENGINES TO THE APU. MAINTENANCE FOUND THE APU LOW PRESSURE SWITCH LEAKING. THE PRESSURE SWITCH WAS REPLACED.