[Bug + Info] CSS Minification Resolves URLs

I’m using a child theme which uses assets from its parent theme. One of them is a style sheet. In this style sheet there are blocks which include relative urls using “url()”.

main_block {
background-image: url(img/main_background.png);
}

Now the problem is that when w3tc minifies the style sheet, it also resolves the url for the child theme this way:

https://example.com/wp-content/themes/child_theme/img/main_background.png

which doesn’t exist because the background image is located in the parent theme at:

https://example.com/wp-content/themes/parent/img/main_background.png

Therefore most of the icons and background pictures are missing. I don’t find any reasons for considering this behavior as desirable or performance enhancing. Also I think this is a regression because at some point in time w3tc was working correctly