Menu Error

There is an issue in the boxed layout where a 3rd level menu item is hidden behind the background. I captured a screen shot here:

https://prnt.sc/l40p2d

Hi Please try this go to Appearance >> Customize >> additional CSS and try to add the following CSS if that do not work kindly send me your website's URL so i can test it. 

Please keep increasing 99 with adding more 9 until it works. 

.top-bar nav ul ul,
.top-bar nav ul ul ul {
       z-index:999999;
}

That didn't work, I kept adding more and more 9s but it still does not work:

http://bsnvet.net.au/

Right now the 3rd level menu is opening in right side of 2nd level menu. Actually when the browser edge is met the absolute positioned menus adjust themselves according to browser width. As here as you are using boxed layout which have fixed width of page 1200px and navigation thinks it still have space in left and right that's why it does not adjust itself automatically well you can add the following CSS which will solve the issue in your Veterinary WordPress theme.

.top-bar nav ul ul ul {
    left:auto !important;
    right: 100% !important;
}

That fixed it, thanks.