Did you replace the runner control box too? ( the silver box that bolts to the bulkhead behind the inlet manifold).
99% of the time when the clip breaks, this box draws the cable in too far, thus stripping the gears inside. Most of the time they completely fail (like mine did) and other times they can just break a couple of teeth causing them to slip.
I've done a bit of looking around for you on focusfanatics (american but some good info) and it seems to be that you need to replace that box. Don't be confused if you look on focus fanatics, because on american focuses, that control box is located under one of the headlights!