Hi gadabra
Hedgehogs can probably safely fall further than we might at first imagine – being cushioned by all those spines.
There might, however, be other explanations for what you describe. For instance the hogs have found another route for their return, or that they are managing to evade the camera. Hogs are notorious for turning up in places where they seemingly couldn’t be (according to cameras). Leading to rumours of teleporting hedgehogs! But cameras are not reliable for catching everything. There is a time lapse between video clips where hedgehogs can often move a fair distance. They can be quite speedy when they put their minds to it!
But if the hogs had fallen down the steps they would likely be rolled up and then having to also unroll again so (unless the camera is very narrowly pointing to the ramp), I wonder why that would not be showing up on your camera images.
Let us know if you solve the mystery!