Getting java.lang.ClassCastException when included WS username token in custom request header while calling a consumed Webservice of some 3rd party.

Soap envelope generated by mendix is as below

Soap request that worked fine in Soap UI

It said like 

com.sun.xml.ws.message.saaj.SAAJHeader cannot be cast to com.sun.xml.ws.security.opt.impl.outgoing.SecurityHeader

Could you please tell what should I do to get rid of these errors?