As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLT 1051, JFK-CUN. RETURNED TO FIELD. FUMES REPORTED AT 14:26 NY FA FROM 12 TILL AFT; FOUND ODOR PRESENT WHEN APU BLEED SELECTED ON. FOUND RESIDUAL OIL ON APU OIL COOLER. NO ACTIVE LEAKS NOTED. REF LOG PAGE 2514210 ITEM 2 FOR APU MEL. NO EVIDENCE OF EXTERNAL LEAKS NOTED. COMPLIED WITH INFORMATION NOTICE 2017-T015D SECTION B. ENGINE IDLE RUN PERFORMED, NO DEFECTS NOTED WITH ENGINE BLEEDS.