What was found
AFTER TAKEOFF, NOTED AIRFRAME VIBRATION IN FWD SECTION OF FUSELAGE. AIRCRAFT RETURNED TO PDX AND MADE AN UNEVENTFUL LANDING. INSPECTED AND FOUND FWD LAVATORY SERVICE DOOR LATCHES LOOSE. TEMP REPAIRED LATCHES AND DEFERRED PER MPM. REPLACED HINGE AND LATCH ASSEMBLIES PER BOEING M/M.