Hi for the issue with attachment link please try adding this given code in your wplms-customizer.php file in wplms customizer plugin :
add_filter('wp_get_attachment_url',function($url){
if(strpos($url, 'sites')){
preg_match('/(\/sites\/[0-9]*){2}/', $url, $output_array);
if(!empty($output_array)){
$url = str_replace($output_array[0], $output_array[1], $url);
}
}
return $url;
});