Goats stop ramming when they pass soul sand or mud

I try to make one youtube farm of goat horns 
Expected:
-in the youtube video they ram in the chichen even when  they pass the soul sand
What happened:
-the goat try to ram but they stop when start the soul sand path, I try to change to mud but the same happend ( they stop when start the path of mud)

Video of reference
https://youtu.be/yuB8-3zs-yU