Hi there, I had this problem as well.
I found out, that in my case it was an issue with my safari browser. With firefox everything works fine. Maybe this helps somebody
Well, lay theme does not currently support menus with submenus. Those menu points will show up, but there are no extra options in the customizer for styling them. So as of now you need to style them yourself by using custom css.
You could do:
.sub-menu{
margin-top: 10px;
}
in "Lay Options" -> "Custom CSS & HTML" -> "Custom CSS for Desktop Version"