In some case (tried using backup/restore libraries server side) loose library generate spaces and endlines in XML-RPC before preparing XMLENC response. This harms a lot XML-RPC debugging because producing a very strange error :

Reserved XML Name

in parsing the payload.

Solution : clean up the incoming raw response from any forward blanck chars :

§196 in mnet/client.php

        if ($this->rawresponse === false) {
            $this->error[] = curl_errno($ch) .':'. curl_error($ch);
            return false;
        }
        
        // eliminates all primary spaces and endlines from unchecked
        // php scripts server side.
        $this->rawresponse = preg_replace("/^[\\s\\n]+/m", '', $this->rawresponse);

        $mnet_peer->touch();

This helps understand why error helpers appear as empty when being displayed in error message.