CSS3 substring-matching selectors not being detected by my sourcemap file

Question

[Fixed] - See bottom of post

I'm not sure if they're just not supported, or if there's something I'm doing wrong. I noticed that it removes the quotes around the attribute, I don't know how or why it's doing this, but maybe this could be causing the issue?

In this example I'm using the substring-matching selector method, and it doesn't work. It's pointing to the generated stylesheet:

In this example I'm no longer using the substring-matching selector method, and it works:

I'm using gulp for my workflow, this is the task that processes my SASS:

gulp.task('sass', function() {
return gulp.src("./src/styles/**/*.scss")
    .pipe(sourcemaps.init())
    .pipe(sass({
        includePaths: ['./src/styles/**/*.scss'].concat(neat)
    }))
    .pipe(autoprefixer({
        browsers: ['last 2 versions'],
        cascade: false
    }))
    .pipe(cssnano())
    .pipe(rename({
        suffix: '.min'
    }))
    .pipe(sourcemaps.write('maps'))
    .pipe(gulp.dest('./dist/assets/css'))
    .pipe(reload({
        stream: true
    }))
    .pipe(notify({
        message: 'SASS task complete',
        onLast: true
    }));
});

Edit: This issue has resolved itself since I restored my default settings in Chrome developer tools. Going to leave the question open though, as I don't actually know what was causing it.

Also, it seems like it was only the element inspector that stripped out the quotes, the quotes still existed in the actual source code.