Bernina 180 Bobbin case spinning

Question

I'll try to describe this as well as I can. There is a black arm at the top of the bobbin case that has a spring attached to it and a little piece protruding that is supposed to fit in a notched area that keeps the bobbin case from spinning. The black arm is loose and keeps allowing the bobbin case (that is what is I am calling the area that has the round center spool that holds the bobbin and it's case)