I tested mine out this morning and the knob is stuck on mine too. While I was sitting there I realized that you can make one with out the maker. All you do is with the needle in the left setting, run a thin line of satin stitching as long as the button hole you want, stop and click it to number 2 and do the tack, turn you whole work, lift the needle and change the needle position to the right, do the line of satin stitching, turn to number 2 setting, tack, and then to 0 and machine knot it. I haven't tried it, but why wouldn't it work?
When I was watching the U Tube instructional video, the man mentioned something about how the fix is done on the knob. I wasn't paying enough attention but it is there for anyone to see. Just google bernina 730 instructional video and it comes up.