How to fix cURL error(7)?

Question

PHP

Hi all! there is a code that interacts with the Yandex API

$method3 = 'GetWordstatReportList';

$request3 = array(
    'token' => $token,
    'method' => $method3,

);
$request3 = json_encode($request3);

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $serv_addr); // set url to post to
curl_setopt($ch, CURLOPT_PROXY, $proxy);
curl_setopt($ch, CURLOPT_PROXYUSERPWD, $proxyauth);
curl_setopt($ch, CURLOPT_FAILONERROR, 1);
curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);// allow redirects
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); // return into a variable
curl_setopt($ch, CURLOPT_POST, 1); // set POST method
curl_setopt($ch, CURLOPT_HTTPHEADER, $post_headers); // set POST method
curl_setopt($ch, CURLOPT_POSTFIELDS, $request3); // add POST fields
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, false);

$response = curl_exec($ch); //получил ответ от сервера
if($errno = curl_errno($ch)) {
    $error_message = curl_strerror($errno);
    echo "cURL error ({$errno}):\n {$error_message}";
}
curl_close($ch);


if ($response === false) {
    die("Произошел сбой. Попробуйте еще раз");
    print_r($response);
    echo $response;

}
$result3 = json_decode($response, true);
if (!isset($result3))
    die("JSON decode error. " . $response);
if (!isset($result3['data']))
    die("Element 'data' not found. " . $response);

And now from time to time (not always!) I get in response cURL error (7): Couldn't connect to server
What could it be and how to get rid of it?