Defense Mode Problem (World War Z: Aftermath)

This is the problem I had while playing this game. In defense mode, a wave of zombies can go, which is only in the image, while it is not materially, and it does not cause damage. The turrets and the military do not shoot at her, the nets do not stop her. But it's annoying when you spent an RPG on it, but in fact there is nothing there. Does anyone know how this can be fixed.