Had a quick look at it, the
<li> are too big for the container so it skips to the second line.
You can adjust the size for the
<li> so it fits on until the media query kicks in and changes the menu to mobile.
Or you could increase the media query to 1200px width so the contact us doesn’t break and it goes into mobile menu at a larger screen size.
I would recommend option 1 though.
Just lower the padding on the object and decrease the font size a tad.