Navigation menu links become unfocusable via a keyboard on narrower viewports

[Igetin]

Describe the problem:

The links in the navigation menu become impossible to focus with via a keyboard if the viewport is narrower than 769 pixels.

Steps to reproduce:

1. Resize the browser window so that the viewport is less than 769 px in width
2. Try tabbing through the links on the page
3. The navigation menu links will never be focused

Observed Results:

This is an accessibility issue. I would expect to be able to tab through the links on the page regardless of my current viewport.