title: admin-ajax.php - the server responded with a status of 500 (Internal Server Error)
body: <p>I've drawn a complete blank with this if anyone can help. I have migrated a website from from a NGINX server to Apache. The installation works fine on NGINX but am running in to the following issue since the migration.</p>
  
  <p>This is a WordPress installation, version 4.9.5 on an Apache server with PHP 7.2</p>
  
  <p>I am constantly getting an error when trying to publish theme customisations.</p>
  
  <pre><code>Looks like something’s gone wrong. Wait a couple of seconds, and then try again.
  </code></pre>
  
  <p>The console shows the following error for file /wp-admin/admin-ajax.php</p>
  
  <pre><code>Failed to load resource: the server responded with a status of 500 (Internal Server Error) 
  </code></pre>
  
  <p>I have taken the following troubleshooting steps to no avail -</p>
  
  <ul>
  <li>Increased memory and size limits to 256M</li>
  <li>Downgraded to PHP 7.0</li>
  <li>Reinstalled core files in /wp-admin and /wp-includes</li>
  <li>Removed .htaccess in case of corruption</li>
  <li>Confirmed no PHP errors using WP_DEBUG (true)</li>
  <li>Confirmed file permissions are as they should be</li>
  <li>Deactivated any non essential plugins.</li>
  </ul>