The central wire pulling through the fibre washer is sadly a regular problem. The fibre the disc is made of seems to be as water resistant as old cardboard. I obtained some black plastic sheet (actually it was a filter housing from an aquarium but anything about 2mm would be fine, its very easy to work, drill a small hole and work (I carefully used a fine grindstone)it into a circle to match the fibre.. the Rolls Royce job would be to strip and pull the wiring through, but I needed a quick repair one weekend so I slit the new washer with a junior hacksaw and slipped it over the wire, the end terminal has a flat just behind the contact to make this easier. The repair has lasted almost 18 months now, I have 2 spare lamps in stock and so modified them the same way. Its water ingress of course that causes the problem!
