I had the same issue. The problem is that W3 cache’s the base url. So if you are using https://www.yoursite.com for one and uk.yoursite.com for the other site you get issues. I fixed it by updating code in W3. I updated the function w3_get_home_url() to always use get_home_url() instead of looking up the cache. The function is in /w3-total-cache/inc/define.php The issue I had was the CDN. Because W3 uses the function below to match and replace. So what would happen is when I went to uk.site.com I would get uk.site.com/www.site.com/css/styles.css
This is my modified function:
function w3_get_home_url() {
static $home_url = null;
//Added this line to always set the home_url
$home_url = get_home_url();
if ($home_url === null) {
$config = w3_instance(‘W3_Config’);
if (w3_is_multisite() && $config->get_boolean(‘common.force_master’)) {
$home_url = get_home_url();
} else {
// This is the problem here
$home_url = $config->get_cache_option(‘wordpress.home’);
$home_url = rtrim($home_url, ‘/’);
}
}
return $home_url;
}