As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNUSUAL ODOR DETECTED NEAR MID CABIN LAVATORY ROWS 18 TO 22 AT LEVEL OFF AND CRUISE. SLOWLY DISSIPATED. ODOR RESUMED DURING DESCENT AND POWER CHANGES. FOUND THE NR 1 ENGINE SERVICE COUPLING LEAKING. REMOVED AND REPLACED THE O-RING, CLEANED AND RE-INSTALLED. NO LEAKS NOTED.