Recently I upgraded my jquery Library for 2.2.4 and it is not working properly when the xhr request type is set to msxml document for internet explorer. Every time it is firing the ajax error method. Hence when we comment it out XMLDocument is sent to the dhtmlx and it is not able to find the child element. It works completely fine in chrome as it sends XMLDOMDocument object to the dhtmlx. Hence support for XMLDocument is requested.
You can send the XML response string instead, it can be used in all places where XML object was used.