As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
SHIP 5648-ATB/FUME- DUE TO STRONG ODOR/FUME THAT DISSIPATED LATER. AIR RETURN DUE TO SMELL. NO ASSOCIATED EICAS MESSAGE. CORRECTIVE ACTION: INSPECTED CABIN/COCKPIT, RAN PACKS AND RECIRCULATION FANS. NO ODORS PRESENT. C/W NO GO ODI PREVENTION & FIM. CHECKED OPERATION OF EQUIPMENT COOLING SYSTEM. REPLACED HEPA FILTERS & LT RECIRCULATION FAN. ALL CHECKS NORMAL.