Main Menu Navigation Links Issue

I’ve updated the slug for my “About Us” page to simply be “about-us”

When I’m on the homepage of my website and I hover over “About Us” within my main navigation bar it shows that I’ll be redirected to “about-us-3”. When I click on that it takes me to a 404 page for obvious reasons, this being it’s not the correct slug.

However, while I’m on the 404 page if I then hover my mouse over the “About Us” within the main navigation menu it shows that I’ll directed to the correct page and slug which is “about-us”. If I click on it then, it actually does take me to the correct page.

In short, when I’m on my homepage the main navigation menu takes me to a different link than when I’m on other pages. I hope this makes sense.

How do I fix this?

Thanks in advance.