Radiobutton checkchanged event not firing properly

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C#

ASP.NET

<asp:RadioButton ID="rdb_previous_post_holder_yes" runat="server"
                                       GroupName="Previous post holder" Text="Yes" AutoPostBack="True"
                                       OnCheckedChanged="rdb_previous_post_holder_yes_CheckedChanged" CssClass="label" Visible="False" />

protected void rdb_previous_post_holder_yes_CheckedChanged(object sender, EventArgs e)
  {
      if (rdb_previous_post_holder_yes.Checked == true)
      {         
          pnl_current_post_holder.Visible = true;         

      }
      else
      {
          pnl_current_post_holder.Visible = false;
      }
  }

I have two radio buttons yes & No. When I click Yes it should do the code below and when No selected it should do the opposite .
It works fine and the checkchanged event is firing for the first few clicks but during testing when the user clicks more than two or three times the checkchanged event is not firing.

Please let me know what should do to rectify it?