i see what your saying mate, but its always a risk young or old and i dont believe in wrapping them in cotton wool.
my new pup here is refusing point blank to go over fences or anything yet, hes just turned 3 months and would rather go under. i will sort that though, hopefully.
My pup was the same but wouldnt climb he would try and push off the top and then something just changed at 6ish months he's 14 months now and he jumps well it's very heart in mouth when he jumps something as speed tho