I Have a drop down list in my Nintex form, Which is populating data from another site SharePoint List using Sp services. I have a hidden text box which is capturing drop down value and connected to list column .  I am not able to save the item, after clicking on save it is redirecting it error page.

Added choice control , Named it as ddlMD (fromat is Drop down list)

Added Single Line text box which is hidden , Named it as txtMD

Could you please any one suggest me what I am doing wrong here.

NWF$(document).ready(function() {

setDropDown();

var dropdown;

dropdown = NWF$("#" + ddlMD);

dropdown.change(refreshddlMD);

});

function setDropDown()

{

var fullWebUrl = "https://test.com/sites/sample/"

var option = '<option value="">Select</option>';

//CAMLQuery: "<Query><Where><Eq><FieldRef Name='ID'/><Value Type='Number'>3</Value></Eq></Where></Query>",

NWF$().SPServices({

   operation: "GetListItems",

   async: false,

   webURL:fullWebUrl,

   listName: "Test",

   CAMLViewFields: "<ViewFields><FieldRef Name='Title'/><FieldRef Name='ID'/></ViewFields>",

   completefunc: function(xData, Status)

   {                   

      NWF$(xData.responseXML).SPFilterNode("z:row").each(function() {

            var title = ($(this).attr("ows_Title"));

         var Id=      ($(this).attr("ows_ID"));

option += '<option value="' + Id  + '">' + title  + '</option>';

});

       $('#'+ddlMD).find('option').remove().end().append(option);

}

});//getListItems

}//Set Dropdown

function refreshddlMD()

{

     NWF$("#" + txtMD).val($('#'+ddlMD + ' :selected').text());

    NWF$("#" + ddlMD).prop('selectedIndex', 0);

    alert(NWF$('#' + txtMD).val())

}