Menu does not show inner elements on mouseover

I extended the sub-theme, without overriding the js files.
When in the home page, on mouseover event, the menu buttons do not show the inner elements.
While, when I am at an inner level in the menu tree i.e. clicking on a first level button, the mouse over works to show the menu child elements.
You can see it live from this test site:
http://www.ilfaro.it/TEST/

I changed the main-menu.js only to apply the fix for mobile menu:
https://www.drupal.org/node/2446843
Do you have any suggestions why this occurs?

Waiting for your kind reply...