Bad response

Hello,

I have a problem with content downloaded by curl, sometimes it's 
downloaded partially.

I have a proxy between server and curl, and seems that all size is 
delivered.

But "size_download" differs of "Content-Length".

Perhaps I am using some function in wrong manner....
Any suggestion?

$maxth = 3;
$channel=1;
$ch=array();
$running=0;
$mcurl = curl_multi_init();

...

(this is a loop) {

$acch= count($ch);
$xmlstr=null;
    if ($acch > $maxth){
                 $cl = ($channel - $maxth);
                 $info=array();
                 while($xmlstr=== null || $xmlstr=== false /*|| 
$info["download_content_length"]!=$info["size_download"]*/){