Problem:
on load when the page layout is boxed the navbar desktop sticky is not full-width.
Generally is not good that it the navbar in this situation needs the document to be ready to look fine.

The problem is even more evident when we have an header image, as in that case the "stickify" sometimes is not triggered on document ready.

That's what happens to the two users reporting this bug at the following link:
https://wordpress.org/support/topic/navbar-not-full-width-until-scroll/