[field url] links to current page rather than the file url.

[field url] links to current page rather than the file url.

My specific instance, I’m trying to use:

[acf_gallery project_gallery]<a href="[field url]">[field image]</a>[/acf_gallery]

The gallery images are displayed fine.
The [field url] works correctly when outside of the<a>(it links directly to the image)
But when it is inside the </a><a> it links to the page it is on, rather than the image.

I have tried switching between PHP 5.3 and PHP 7
I am using WP 4.5.3
ACF Pro 5.3.8.1
CCS 3.6.7

Thanks

https://wordpress.org/plugins/custom-content-shortcode/