I ran in to the same issue (using PHP, CURL instead). When creating a Remote Destination for a Remote Profile the AXL schema auto inserted "dualModeDeviceName" nil setting in the response and generated the error regardless of the value or no value set in the field. I had to edit the 10.5 AXLsoap.xsd file. Under the XRemoteDestination -> dualModeDeviceName I set the minOccurs setting from 1 to 0. Now AXL schema doesn't inject this setting into the response and everything builds correctly.