Submenu causes menu tree to disappears when mouseover

Hi @ulfert,

This is the default behavior of Bootstrap framework that we have used in our theme. You can confirm it on the following Bootstrap framework nav menu demo page.

http://getbootstrap.com/examples/navbar/

If you want to make the top level menu link visited on clicking on it then you can use the solution posted in the following reply.

Best Regards,
Movin