I have a Janome and I love the walking foot when I'm doing anything with batting. I don't understand what arm fell apart. I'd take it back to the store where purchased and ask for a replacement and another demonstration. Then sit down and work with it while you are still there so you totally understand how it should work. Take it off the machine and put it back on while there! Something's not right here. For the one on the Janome, be sure the little arm is over the thumb screw that holds the needle in. Very important to get that little flapper-thing in the right place.
Has anyone used their walking foot on a featherweight? My store said the one for the Janome will work on my FW because they both are low shank machines. I haven't gotten the FW out to see if it works though. Comments, please.