ASP.NET MVC Submit Button Value became null on subsequent click

Consider the following html with three submit buttons:

@using (Html.BeginForm("Process", "Part4", FormMethod.Post, new { id = "submitForm" }))
{
    <select class="form-control" name="lbToolingID" id="lbToolingID">
    @foreach (var toolingID in toolingIDList)
    {
        <option value="@toolingID">@toolingID</option>
    }
    <input class="btn btn-primary" type="submit" name="btnAction" value="Add Tooling" />

    @* Selected tool will be added here on the [Add Tooling] button click *@
    <table>
    @if (Model != null && Model.M_PartTooling_List != null && Model.M_PartTooling_List.Count > 0)
    {
        for (int i = 0; i < Model.M_PartTooling_List.Count; i++)
        {
            <tr>
                <td nowrap>
                    @Html.ActionLink("Remove Location", "Remove", new { @id = Model.M_PartTooling_List[@i].ID }, new { @class = "btn-sm btn-danger" })
                </td>
                <td nowrap colspan="2">
                    @Html.HiddenFor(model => model.M_PartTooling_List[i].ToolingID)
                    @(Model.M_PartTooling_List[i].ToolingID)
                </td>
            </tr>
        }
    } 
    </table>

    @* Once done these buttons will add the records into database *@
    <input class="btn btn-success" type="submit" name="btnAction" value="Save & Return To List" />
    <input class="btn btn-success" type="submit" name="btnAction" value="Save & Continue Create" />
}
...
...
@section Scripts 
{
    @Scripts.Render("~/bundles/jqueryval")
}

The following is the action :

[HttpPost]
public ActionResult Process(M_PartViewModels m_PartViewModels, string btnAction, string lbToolingID)
{
    if (btnAction == "Add Tooling")
    {
        AddPartTooling(m_PartViewModels, lbToolingID);

        return View("Create", m_PartViewModels);
    }

    CreatePart(m_PartViewModels);

    if (btnAction == "Save & Return To List")
    {
        return RedirectToAction("Index");
    }

    return RedirectToAction("Create");
}

On the first time clicking the Add Tooling button, it is working fine, we can see that on breakpoint the value of btnAction is indeed Add Tooling :

But on the second time clicking the Add Tooling button or any other two buttons, somehow the value of btnAction became null :

We have already inspect the said button in the browser and we can see that value of the button still intact :

Can somebody point out what was the cause of this and how to work around this?

I know we can work around this using jQuery but we wanted try this with minimal jQuery coding if possible.

UPDATE

Removing the reference to this script got the page to work as intended but it disables any other (remote) validations that we had:

@section Scripts 
{
    @Scripts.Render("~/bundles/jqueryval")
}

Will look more into this. Possibly if we can disable the call to remote validation temporarily on Add Location button click.

UPDATE 2017-06-22 0017 WITH OK SOLUTION - jquery.validate* is the culprit?

This may not be the solution I would like it to be but as long as it is working I am OK with this.

Since we already knew that removing the

@Scripts.Render("~/bundles/jqueryval")

made the page work as intended.

This is the bundle definition by the way :

bundles.Add(new ScriptBundle("~/bundles/jqueryval").Include("~/Scripts/jquery.validate*")); 

I decided to ditch the remote validation

[Remote("CheckPartID", "Part", AdditionalFields = "PartID_Ori", ErrorMessage = "Part ID already in use!")]

defined in my model annotation and port the validation into my action instead :

    [HttpPost]
    public ActionResult CreateProcess(M_PartViewModels m_PartViewModels, string btnAction, string lbToolingID)
    {
        ViewBag.VMainMenu = GetMenu();
        ViewBag.ToolingIDList = GetToolingID();

        CheckPartID(m_PartViewModels);
        CheckPartDesc(m_PartViewModels); 

        if (btnAction == "Add Tooling")
        {
            AddPartTooling(m_PartViewModels, lbToolingID);

            return View("Create", m_PartViewModels);
        } 

        if (ModelState.IsValid)
        { 
            // Do some DB insert stuff

            if (btnAction == "Save & Return To List")
            {
                return RedirectToAction("Index");
            }
            else
            {
                return RedirectToAction("Create");
            } 
        }

        return View("Create", m_PartViewModels);
    } 

    public void CheckPartID(M_PartViewModels m_PartViewModels)
    {
        if (m_PartViewModels.M_Part.PartID != m_PartViewModels.M_Part.PartID_Ori)
        {
            var routingID = db.M_Part.Where(u => u.PartID == m_PartViewModels.M_Part.PartID).FirstOrDefault();

            if (routingID != null)
            {
                ModelState.AddModelError("M_Part.PartID", "Part ID already exists."); 
            }
        }
    }

    public void CheckPartDesc(M_PartViewModels m_PartViewModels)
    {
        if (m_PartViewModels.M_Part.PartDesc != m_PartViewModels.M_Part.PartDesc_Ori)
        {
            var routingID = db.M_Part.Where(u => u.PartDesc == m_PartViewModels.M_Part.PartDesc).FirstOrDefault();

            if (routingID != null)
            {
                ModelState.AddModelError("M_Part.PartDesc", "Part Description already exists.");
            }
        } 
    }

While I felt not entirely satisfied with this solution (where the validation only fires on submit instead on keyup) but since it is working as intended will use this for now.

Will update this once found better way.

Thank you for your kind attention guys. I really appreciate it. :)