ASP.Net MVC: Send checked CheckBox value to Controller on submit click using jQuery

I work on asp.net MVC application I face issue when change check box (Yes to No) OR (No to Yes)

not detect value true or false correctly .

I have two check box

Yes represent true value

No represent false value

I don't need to change checkbox to radio button because this is user requirement as checkbox .

when select Yes or No for first time it send value correctly

but when I select Yes or No for second time it not send value correctly and send only value false to approve button when select Yes or No .

What I Try

1 - User UI for Yes or No

<td style="width: 50%; font-weight: bold; padding-top: 10px;">
      @Html.Label("Did you try to retain the staff?", htmlAttributes: new { @class = "control-label col-md-5" })
      <div class="col-md-7">
          <input type="checkbox" id="RetainStuff" name="RetainStuff" value="true" class="retaindtuff-checkbox" @(Model.RetainStuff == true ? "checked" : "") />
          Yes
          &nbsp;&nbsp;
          <input type="checkbox" id="RetainStuff" name="RetainStuff" value="false" class="retaindtuff-checkbox" @(Model.RetainStuff == false ? "checked" : "") />
          No
      </div>
  </td>
<a id="approveControlsId" onclick="submit();" class="btn btn-primary" style="min-width: 100px;margin-top:5px;"><i class="glyphicon glyphicon-ok"></i> Approve </a>

2 - when change Yes or No check box to get value true or false of retain stuff checkbox i use jQuery as below :

$('.retaindtuff-checkbox').on('change', function () {
     $('.retaindtuff-checkbox').not(this).prop('checked', false);
     var selectedValue = $(this).val();
     $('#RetainStuff').val(selectedValue);
});

3 - when click approve button value of check box not send correctly to submit() function

function submit() {

    var ResignationRequester = new Object();
    ResignationRequester.RequestNo = document.getElementById("RequestNo").innerHTML.trim();



    var RetainStuffElement = document.getElementById("RetainStuff");

    if (RetainStuffElement) {

        var RetainStuffElementExist = document.querySelector('input[name="RetainStuff"]:checked');

        if (RetainStuffElementExist && RetainStuffElementExist.value === "false") {
            ResignationRequester.RetainStuff = RetainStuffElementExist.value;

            ResignationRequester.RetainStuff = null;
            return false;
        }
        else if (RetainStuffElementExist) {
            ResignationRequester.RetainStuff = RetainStuffElementExist.value;

        }
        else {
            ResignationRequester.RetainStuff = null;

            return false;
        }
    }
    else {
        ResignationRequester.RetainStuff = "";

    }

    if (ResignationRequester != null) {
        $.ajax({
            type: "POST",
            url: '@Url.Action("ApprovalIndex", "Resignation")',
            data: JSON.stringify(ResignationRequester),
            contentType: "application/json; charset=utf-8",

            datatype: "html",
            success: function (response) {

            }

        });
    }
}

4 - action result calling ApprovalIndex on resignation controller

[HttpPost] 
public async Task<ActionResult> ApprovalIndex(ResignationRequester REQ) 
{ 
    //update approve status 
} 

so why checkbox yes or no working on first time only