Here comes another post of why you need to ride Campagnolo instead of Shimano. I have replaced numerous derailleur cables (rear) over the years. The cable snaps half an inch from the pill on the end of the cable. Why, cheap cable, end of use cycle, storing the bike frequently after rides in a low gear on the cassette. The latter keeps constant tension on the cable, stretching it over time.
One of the local racers had a cable snap a couple of months ago. I replace the cable but was unsuccessful retrieving the broken section of cable. It had fallen into the body of the Dura Ace shifter. Problems from that were waiting to arise. He had shifting issues recently so now was the time to disassemble and retrieve the shrapnel.
While I don't have any pics from the service but I can pass a few thing onto you. First off, if you don't have the mechanical aptitude to disassemble and reassemble anything, don't proceed, send the shifter back to Shimano for service of find someone that has their game on. My saving grace was a dental pick. I have a 5 pack that a dentist/customer of mine gave me. They are the real deal and are great for resetting springs and such that pop out of place during rebuilds. Ergos too.
Loosen the lever axle set screw and carefully remove the lever axle with a drive punch and rubber mallet. There is a main pivot bolt that runs through the shift mechanisms. A nut located behind the shifter name plate/external return spring cover is removable and is required to be removed in order to pull the shift paw/mechs slightly apart to retrieve the snapped section of cable. When pulling the assembly apart, I guarantee that the high gear selector lever will go limp on you. If you look closely where the black lever runs up into the shifter body, there is a small wound spring that has popped out of its retention location. Break out the dental pick. The spring has one end bent north and the other end bent south. Feel around the north side where the spring rests and locate the hole that the spring tab goes into. Install it and hold in place with the end of the dental pick. Gently pull center pivot bolt a couple of millimeters away from the end of name plate area, turn and line up the south spring tab into the hole. Twist the other way and slide the mechs and bolt together. Got that? LOL!
So the hood wink of all of this is that Campagnolo doesn't have an enclosed shifter body that could potentially trap a broken section of cable. The accessibility of the cable is all open air. Easy to retrieve.
I am praying that Campy make available to IBDs their 'G' springs that are going into their 'Red' Pro shifters. It's a heavier spring tension, nice! Less chance of mis-shifts too.