Xenforo Libmemcached xenforo

I'm using the following cache in my xenforo config.php file

Code:

//$config['debug'] = 'true';
$config['cache']['enabled'] = true;
$config['cache']['cacheSessions'] = true;
$config['cache']['frontend'] = 'Core';
$config['cache']['frontendOptions'] = array(
                                        'caching'                      => true,
                                        'automatic_serialization'      => false,
                                        'lifetime'                     => 0,
                                        'cache_id_prefix' => 'bees',
                                        );

$config['cache']['backend'] = 'libmemcached';
$config['cache']['backendOptions'] = array(
    'compression' => false,
    'servers' => array(
        array(
            // your memcached server IP /address
            'host' => 'localhost',
            
            // memcached port
            'port' => 11211,
            'persistent' => 'true',
            'weight' => '1',
        )
    )
 );

It seems to work for a short while before giving me a server error message. It worked on my old server, so what do I need to check thats different?