Ok for anyone else running into this issue, I looked through the plugin code and found this line (309):
wp_enqueue_script('emc2-pm-admin-js', WP_PLUGIN_URL.'/'.str_replace(basename( __FILE__),"",plugin_basename(__FILE__))."admin.js?v=".$cachebuster);
Change that line to this:
wp_enqueue_script('emc2-pm-admin-js', plugins_url().'/'.str_replace(basename( __FILE__),"",plugin_basename(__FILE__))."admin.js?v=".$cachebuster);
That will fix it. The problem is the use of WP_PLUGIN_URL. I hope plugin creator will fix this in his next update.