There was a problem with the AJAX request…

There was a problem with the AJAX request, we were expecting a serialized response, instead we received: <data>

There are generally only three scenarios where this error occurs:

1. PHP errors or notices are included in the POST response. Please check these error messages and either fix or suppress these notices accordingly.
2. The remote plugin is out of date, please ensure both the local and remote websites are running the latest version of WP Migrate DB Pro.
3. There is custom code on the remote that redirects away from admin-ajax.php very early in the admin request flow (e.g. admin_init hook).