As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
BURNING RUBBER SMELL AFTER T/O DISSIPATED IN CRUISE RETURNED AT TOP OF DESCENT, FA REPORT MOST NOTICEABLE IN AFT LAV. MAINTENANCE PERFORMED HIGH POWER ENGINE RUN, NO SMELL. GAINED ACCESS INSPECTED RECIRC FANS & REPLACED FILTERS NO DEFECT FOUND.