Thanks Yuval, I contacted the support team and they were helpful.
In the end I figured out the issue and it was on my side. For others interested or experiencing something similar when working with php, it was the way SimpleXML handles CDATA, and the solution was to change the way the SimpleXML instance is created:
Code:
Original:
$oXML = new SimpleXMLElement($result);
New:
$oXML = simplexml_load_string($result, 'SimpleXMLElement', LIBXML_NOCDATA);
Thanks for your help.