They really love that ridge!
Falling doesn't USUALLY hurt them. But I always wonder if they like that secure feeling so well that they will neglect to get needed heat in their warm hide.
I would remove the snake from the cage for a couple of days. Then get some silicone seal such as used to construct aquariums. I would run a fairly thick bead of it around the ledge, and then "smush" it a little as you would when caulking (I suppose caulk would work as well). Let dry, and air out for a couple of days. If there is still too much room, you might have to run another bead, and dry.
I should mention that I have never actually done this because I don't use aquariums. I have suggested it to a couple of customers, but never heard back whether they actually did it, and whether it worked. But I THINK it should. If you decide to try it, be sure to report back so we can tell others if it works.
It is a problem that will eventually solve itself as the baby grows and can no longer fit on the ledge.
Good luck!