"fake" fileysstem direct mode.

fluent-demo-force-direct.php

<?php
/*
Plugin Name: Fluent Demo - force direct
Plugin URI: #
Description: Forces wp to think it has direct filesystem access during ajax and admin requests.
Author: No Half Pixels Ltd
Version: 1.0.0
Author URI: http://nohalfpixels.com
*/
add_filter( 'filesystem_method', function($method){
  if(is_admin() || is_defined('DOING_AJAX') && DOING_AJAX){
    return 'direct';
  }else{
    return $method;
  }
});