I understand where you are coming from, 2 examples of how a horse can leapfrog up or down could be barrier and pace. After scratchings I adjust barriers and this can have enough effect on my ratings to cause a horse to jump more than one spot.

Also pace plays a role in my ratings so if for example there were 2 recognised leaders in the race and one of them were scratched (say it was an outsider but one that could put some pace in the race), this could open up the race for the other leader to get a soft run in front and could push its ratings up while also pushing a highly rated backmarker down a bit.

Cheers,

Mat.