There should be a middle position on your needle up/down lever. For darning/free motion you need to use the middle position. You have the ablility to lower the needle and then raise the needle lever and then if you look you have a middle position also which is what you should be using. That's how is works on my 7570 so hopefully it is the same way on your expression 2. If you have a manual look up darning and it should explain how to do this properly.
Hope this helps....