As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
STRONG RUBBER BURNING SMELL THROUGH CABIN AND COCKPIT AROUND 24,000 FEET FOR ABOUT 2 MINUTES. PERFORMED GVI OF #1 AND #2 PACK AREA, PRECOOLER AND INTERIOR OF CABIN AND COCKPIT WHILE APU OFF. NO DEFECTS NOTED. TROUBLESHOT ABNORMAL SMELL. NO RUBBER BURNING SMELL NOTED AFTER RUNNING BOTH PACKS SEPARATELY. NO DEFECTS NOTED.