Hey mate I had a set of Kershers and the same happened to me, what you need to do is get a small metal drill bit and I mean small, slowly drill it in to the piece of stuck bolt,if this turns when you do it then reverse the drill and it may come out, if not drill a small hole then get a small flat head or some thing very small and square and tap it in. Then it should slowly turn as you un screw it, Hope you understand what I mean, but dont worry if you cannot do it as It will only take someone with the right tools a couple of mins. Mine did. Good luck.