I’m adding to this old link because I had the same problem and found an easier way to resolve it without a complete break down as described in the aforementioned U Tube clip. I still had to remove the front cover very carefully with very thin screwdrivers, you will have to add a little leverage so be careful. Having done that and checking that the spring positions on both feet inner clips looked to be in the same position when looking down on them but obviously reversed for either side I was then able to position the remaining foot so that it was inline with the disc body then use my finger nail to hold the opposite spring clip in the same position but again in reverse. I was then able to push the foot that had come away back into the spring fitting quite easily when in line with the disc and then it was just a matter of carefully clipping the cover back on making sure that it is lined up correctly.
It worked for me and hopefully will help others with a similar issue. It is worth checking out the U Tube clip just to see how the disc is put together before taking the plunge.
Hope that helps.
