There was a design defect on the first run of X-Faders on the Xone 62/64. The piece of metal that used to house the plastic part of the fader was too thin for it's length, so A&H got Penny & Giles to redesign it.
If you're lucky (like me) your mixer was still under warranty when this problem surfaced, and they will replace it free of charge, otherwise, you're looking at about £100 to replace it.

As for questioning the build on A&H products, you must be mad. EVERYTHING will become defective over a period of continued usage with moving parts. Thankfully A&H components are high quality and all replaceable which means that you can just fix the bits you need to, as opposed to shelling out for a brand new mixer everytime a predictable defect occurs (especially on cheap shit mixers.)

Hope this is useful.