I started with Belle and quickly discovered that getting the correct end of the tunnel (white circle #4) was a very difficult thing. The first time, Belle took the dogwalk, and on our other attempts, she took the wrong end of the tunnel (white square #4). I brought out Dusty and figured we'd just mess around and do what we could do with this exercise. To my amazement, he had absolutely no trouble getting the correct entrance.
I decided to try this exercise with Belle again and tape it. Maybe I could see what was going wrong. I never did figure why it didn't work, but more importantly, we eventually got it right. Here's the video:
My statement above brings to mind advice from Fred Brattain (The Art of Getting Out of Your Own Way). When you analyze a run, don't think about what you did wrong; visualize what you should have done. It is a subtle distinction; but one that is worth making.