I want to teach my girl Dakota to back up. The problem is that I'm getting interference from other things I've taught her. I taught her 'front' and now, when I get in front of her and start trying to back her up she sits. Everything I try to back her up, she sits. I can bring her forward and get her to stand, but as soon as I reverse, she sits. How can I get past the connection between back-up and sit-down? Should I give up on 'back' for now?