I've had a couple of problems with my XTR shadow mech due to what appears to be the carbon cage warping over time so it doesn't run quite straight. It's not been whacked by anything just seems to be an inherent issue with the carbon. I've also got a problem now where the chain comes of the lower Jockey wheel on the smaller gears on the cassette. Twisting the cage doesn't seem to help and I can't work out what's causing it. Any ideas?

I've heard that the cage flexes compared to the metal cages – not tried it yet but you can cable tie the bottom of the cage together which makes it stronger at the bottom – there are two holes near the bottom you can use.