ASP.NET 'WebForm_PostBackOptions' is undefined error - Only occurs in server, for one page

Question

I've been assigned to fix some issues in our legacy system, which is created using Asp.net 2.0. This application is created to run on IE lower versions (v5.0/v7.0/v9.0).

The issue is, when I tried to click on a link of the page, it gives me the error 'WebForm_PostBackOptions' is undefined. For the naked eye, it seems like the click event is not even triggering, so, I can only see the error when I open the console (F12) of IE.

The problem is, this works fine in my local environment, and even in another testing environment. This only happens in our Live server, only in one section of a single page; make me wonder whether there are any version incompatibilities.

below are my relevant .aspx and .cs codes.

.aspx

<asp:Repeater Runat="server" ID="rptCustomers">
    <ItemTemplate>
        <asp:Label Runat="server" ID="lblCustomerID" Visible="False" Text='<%#DataBinder.Eval(Container.DataItem, "id")%>' />
        <asp:LinkButton Runat="server" ID="lbtnCustomer" CommandName="SELECT CUSTOMER" Text='<%#DataBinder.Eval(Container.DataItem, "name")%>' /><br>
    </ItemTemplate>
</asp:Repeater>

.cs

private void rptCustomers_ItemCommand(object source, RepeaterCommandEventArgs e)
{
    if(e.CommandName == "SELECT CUSTOMER")
    {
        if(((Label)e.Item.FindControl("lblCustomerID")).Text == "")
        {
            ViewState["Customer"] = Guid.Empty;
        }
        else
        {
            ViewState["Customer"] = new Guid(((Label)e.Item.FindControl("lblCustomerID")).Text);
        }
        RebindData();
    }
}

I would really appreciate if someone could give me some kind of a solution, or an explanation for this. Thank you in advance

Answer 1

OK so I found an answer for this if anyone faces the same issue one day. It's something to do with the server IIS, and after I added the tag CausesValidation ="false" to my code segment, the issue was resolved.