As I pulled pieces of the past, I soon realized that in the beginning I asked my dog, Bo, to Sit and stay at the start line. But he soon began to lean and scoot, so I changed to a Down and stay command. He did this for a while until he began to slowly crawl and creep. I would then walk away for a lead out, but I would still face her, by being face to face, that would help him to hold his position, at least for a little while. Before I knew it I started getting breakaways, he was no longer interested in waiting at the starting line, the second I started to step away from his side, he would be off. That's when I decided to pull him from trialing.
The question I had to ask myself was why did her behavior get worse at the start line? The answer is that I started to negotiate with my dog, way back when she first moved from the Sit-stay, I should have done was to make it clear that the Sit -stay was the one and only behavior that would bring the reward of running his agility course. What I mistook as, "I'm asking too much for my edgy dog to Sit-Stay on the line." he took as, "Dad, doesn't really mean what he says when we're in this fenced ring with lots of people watching." So, he began to test each and every behavior I asked for on the line. What you have to remember it that dogs will do what we allow.
If your dog ever begins to break its start-line stay, whether that is a stand, sit, or down, STOP training immediately. Don't run your run. I know you've already paid your entry fees, but you will be spending much more time and money fixing the problem when it gets worse, and it eventually will. For some dogs, taking them off the course is deterrent enough to get back on track. Other dogs may be more difficult and may require you to "train" your stay in the ring.