This has been a problem area for many years - I had a similar incident in Riyadh in the mid 80's - fortunately with no fire damage. The pylon area drains were blocked with high temp sealant on assembly and the leak from the Wiggins coupling filled up the pylon. Some months later I had a letter from Boeing asking for a report which I gave them - the result was a check to ensure that all pylon drains were clear. The cause of the leak was hardening of the O ring seals in the fitting - when I removed them they were like hard plastic and square in section. The fitting concerned is used in many locations on 747 aircraft for Fuel lines and on some SP aircraft for hydraulic lines - it is used where some flexibility is required as in this case between pylon and front spar.On several occasions I have seen incorrect assembly which fortunately did not result in fires,in my opinion this type of coupling is a hazard which is of dubious reliability.