For most satisfying results, particularly if you are new at making things like this, and/or if you are not a mega-experienced wire-worker, pay close attention to the sizes for stones and wires before you begin, and use what Eni recommends so that your project will come out pleasingly and you will still have all your hair on your head. if you do as I did, and not notice the sizes of stones and wire recommends, your project will not turn out like the picture, and may even be unsalvageable (at minimum, it will require lots of creativity on the part of you, working with your own brain, to make something you can live with(after 2 years, I am still working on my first ring, which was made with two big a stone, and has repeatedly broken. This time, I will win!)
After that first ring, i followed Eni's instructions to the T and everything has turned out perfectly.

If the cab seems to be snapping off of the setting, then it probably means that the setting is too low (too shallow) to hold the cab. Cabs can be thicker or thinner, so you need to adjust for their size.

The solution is to make the spirals slightly bigger, and that will naturally make the entire setting taller -- enough to cover a thick cab.