In the project I'm working on, I was losing some of my styling when the project is built minified. The two main things I was losing was a top padding on a container to bring content below a nav bar and a heading styling.
I noticed all the troublesome styles were at the bottom of my stylesheet so I moved them to the top and voila, they worked. I then started looking through my other styles trying to figure out if any would be causing issues. I came across a class style that I wasn't actually using but that was in error (The background image URL for an SVG was wrong, so showing red). I then moved that style back up, above the previously troubled (now fixed) styles and the problem returned.
So I am wondering if there's a bug where minification will stop when it hits any error and then lower down styles are ignored.
Here is the error-ing style. If I disable the checkbox and build minified, all works. So it's something to do with processing enabled, badly formatted styles.
background-image:url(data:image/svg+xml,<svg preserveAspectRatio='none' viewBox='0 0 100 16' fill='rgb(5,58,127)' fill-opacity='1'><polygon points='0,16 100,16 100,0'></polygon></svg>);