多次刷新后phpcurl失去连接

我使用这段代码访问myOwncloud服务器，它工作正常，但是如果我刷新页面，我会得到这个错误“请求的URL返回错误：401” 如果我等5分钟或者其他什么的话，它又能工作了 知道为什么吗

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $this->url.($this->path ? '/'.$this->path : ''));
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); /// 1
curl_setopt($ch, CURLOPT_TIMEOUT, 30);

curl_setopt($ch, CURLOPT_USERPWD, "$this->username:$this->password");

//PROPFIND request that lists all requested properties.
curl_setopt($ch, CURLOPT_CUSTOMREQUEST, 'PROPFIND');

curl_setopt($ch, CURLOPT_FAILONERROR, true); // Required for HTTP error codes to be reported via our call to curl_error($ch)
$response = curl_exec($ch);

if (false === $response) {
    $response = curl_error($ch);
}

curl_close($ch);