Lines 833-834 of Snoopy.class.php contain:
if(!empty($body))
$headers .= "Content-length: ".strlen($body)."\r\n";
And Lines 997-998
if(!empty($body))
$headers[] = "Content-length: ".strlen($body);
When pulling from a new server (IIS) it resulted in a "bad length" result even if there was no body, and required Content-length: 0.
By removing lines 833 and 997 so to always write the Content-Length it worked again perfectly.