Just a question. What is the mod for? Not what does it do, I know that, what is it that you want it to do? Do you have a focus frame so you can see who is your focus? When you run the focus macro, does the correct person end up as your focus?
So if you have the correct focus, then the stop macro is kinda confusing. It only stops if you don't have a focus and you push shift. Each condition is put together with an AND. If you wanted an OR, try:
/stopmacro [target=focus, noexists] [mod:shift]

Hope that helps. Good luck.