This happens randomly, sometimes I can not jump over small fences or character level walls, simply the space bar jump become unresponsive, in other occasions, some knee level fences (concrete ones) are climbed instead of jumped over by my character. As I said before, I know vaulting is related to stamina level but I am sure it was full but the problem remains, I tried experimental before the modification of stamina consuption and it worked perfectly, but after the change it's not working properly. A pitty really. It is vital sometimes not to struggle to jump over a small fence or even a climbable one, and with this problem, if you're being persued by zombies or other players it can cost your life.