Click on menu -> sometimes scroll, sometimes jump

I work with the bedj template and my problem is that a click on the original menu buttons led to a nice scroll to the respective section.

now i added other menu buttons but the scroll is gone. i dont see a difference between the original buttons and mine,more specifically i dont even see the parameter for the scroll effect. there is also no custom css written for it.

So what i can i do?

thanks for your help! :)

Florian