Why is the xml content not fully passed through guzzle?

Question

XML

Hello.
I get using guzzle xml from a remote resource.
For some reason, the result $response->getBody()->getContents()is a line without the first line of xml
(example: <?xml version="1.0" encoding="UTF-8"?>)..
And, as I understand it, because of this

new SimpleXMLElement($response->getBody()->getContents())

is an empty object?
Or am I parsing the xml response somehow wrong?
Thanks in advance!