Some <td> borders have more thickness in dataTable

I am using jQuery Data Table in Bootstrap. table is getting fine. But Some td borders have more thickness than others. Don't know the exact reason. Here I am showing screenshot of my table. along with code used

  <link rel="stylesheet" type="text/css" href="https://cdn.datatables.net/buttons/2.2.2/css/buttons.dataTables.min.css">
    
    <table class="table">
      <thead>
        <tr>
          <th scope="col">#</th>
          <th scope="col">First</th>
          <th scope="col">Last</th>
          <th scope="col">Handle</th>
        </tr>
      </thead>
      <tbody>
        <tr>
          <th scope="row">1</th>
          <td>Mark</td>
          <td>Otto</td>
          <td>@mdo</td>
        </tr>
        <tr>
          <th scope="row">2</th>
          <td>Jacob</td>
          <td>Thornton</td>
          <td>@fat</td>
        </tr>
    </tbody>

</table