Background Images Not Showing

Hi,

All seems to working fine except for background images which are not showing once the page is cached.

I’m on a dev server so can’t give you access but the css is :
background-image: url(https://xxxx.xxxx.co.uk/wp-content/uploads/headway/cache/https://xxxx.xxxx.co.uk/wp-content/uploads/2016/09/contact-banner.jpg);

No other minification or caching plugins are active. Any thoughts based off this limited info I can provide you!

I can provide you with a link private to the dev site if required.

Thank you.