What was found
ACFT CABIN HAS RANCID ODOR. FULL LAV SERVICE COMPLETED. WALKAROUND FOUND VERY STRONG ODOR COMING OUT OF OUTFLOW VALVE. GAINED ACCESS TO BACK OF OUTFLOW VALVE & LAV SERVICE PANEL. IDENTIFIED STRONG FOUL ODOR. LIKELY COMING FROM THIS AREA. IDENTIFIED SMALL AREAS OF DRIED LAV JUICE RESIDUE ON INSULATION BLANKETS. REMOVED LAV K TOILET SHROUD FOUND A BUNCH OF OLD NAPKINS COVERED IN BLUE JUICE. CLEANED BLUE JUICE & NAPKINS IN LAV K . ODOR CONTINUES FURTHER T/S REQUIRED. CALLED FOR LAV SERVICE. DUMPED & SERVICED AFT LAVS TWICE. COULD NOT IDENTIFY ANY LEAKS FROM TOILET TANK OR DUMP CHUTE. R & R DETERIORATED SECTION OF THE INSULATION BLANKET ABOVE OUTFLOW IAW AMM 25-50-07. VENTED OUT ODOR. NO ODOR NOTED IN CABIN.