Mobile Plug-in: Header issues

So I was able to edit the header for mobile detect just by adding the hamburger icon and search icon.

I also learned how to add my own background to the header too.

Question, everything works great and looks great but when viewing the site through Facebook’s internal web browser the header background is gone. If you turn your phone side ways you’ll see the background image is there but very stretched.

Been trying to figure out ways to fix it. I checked my site on all browsers using a device browsers extension to trick my site so I can see if there was any issues. None. This only happes on Facebook. Would love to see your suggestions.

https://justdisney.co
facebook.com/JustDisney
You’ll see the article links on FB page.

Thanks!