file_get_contents sometimes works, sometimes doesn't - php

Question

I am in Ubuntu 14.04 with a Nginx server and my code is made with symfony2.
I have a simple API that returns a Json response.
I am trying to access this page with another page with the file_get_contents:
public function formAction()
$url = 'http://example.com/api/link/';
$options = array(
'http' => array(
'header' => "Content-type: application/x-www-form-urlencoded\r\n",
)
);
$context = stream_context_create($options);
$result = file_get_contents($url, false, $context);
return ($result);
}
But sometimes it works, sometimes it doesn't!
I made a loop to see the frequency:
It looks like it works 63/100 and 250/1000. (As mean value)
I got this error when it doesn't work:
Warning:
file_get_contents(http://example.com/api/link/):
failed to open stream: HTTP request failed! HTTP/1.1 404 Not Found in
/srv/www/path/to/my/file.php
on line 69
This started to happen when I reboot my instance in Amazon web server, so I don't know if I should make some configuration change now. I've tried to use curl but same problem.
UPDATE
If I try to access the page in the browser it always work immediately.

Answer 1

I discovered what it was:
In my OVH hosting I changed the ipv4 of my dns.
But I didn't change the ipv6.
So sometimes when I tried to access the site the calls were being redirected to the right ip (the path showed in ipv4) and sometimes the old wrong one (the path indicated by the ipv6)