In Duck Racing, it shouldn't be possible to go back if you're on say the first 5 squares of the board. Currently this allows you to jump to square 29 or 30 and immediately finish a lap.

Hello,
I don't think I fully understand your message, but if I got it right, are you trying to say that if you are in, for example, lap 1 and square 1, and you use a card that allows you to go back a few squares, and then advance to square 1 again, you will finish a lap?
If so, then this is not going to happen.
When you go back, you are effectively going back to the previous lap, even if one doesn't exist. In my example, if I am on lap 1, square 1, and I use a card like removal to go back 3 squares, I will instead be on lap 0. Advancing from 30 will thus just put me back in the first lap.

Hope that helps.

Oh really? I thought it was allowing you to immediately complete laps.