The icon button collapse paint wrong to the navbar

[vincenzopalazzo]

I have one problem with the component NavBar External content.

With this code

<div class="jumbotron bg-dark">
  <h1 class="display-4 bg-dark text-color-lime title-demo">SpyJSBlock Demo</h1>
  <div class="pos-f-t">
    <div class="collapse" id="navbarToggleExternalContent">
      <div class="bg-dark p-4 border-0">
        <ul class="nav nav-tabs justify-content-center bg-dark border-0" id="myTab" role="tablist">
          <li class="nav-item border-0">
            <a class="nav-link active bg-dark text-color-lime border-0" id="home-tab" data-toggle="tab" href="#home" role="tab" aria-controls="home" aria-selected="true">Demo</a>
          </li>
          <li class="nav-item">
            <a class="nav-link border-0 text-white bg-dark" id="profile-tab" data-toggle="tab" href="#profile" role="tab" aria-controls="profile" aria-selected="false">Benchmark</a>
          </li>
          <li class="nav-item">
            <a class="nav-link border-0 text-white bg-dark" id="contact-tab" data-toggle="tab" href="#contact" role="tab" aria-controls="contact" aria-selected="false">Info</a>
          </li>
        </ul>
      </div>
    </div>
    <nav class="navbar navbar-dark bg-dark">
      <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarToggleExternalContent"
              aria-controls="navbarToggleExternalContent" aria-expanded="false" aria-label="Toggle navigation">
        <span class="navbar-toggler-icon"></span>
      </button>
    </nav>
  </div>
</div>

I have this effect on the button

I attended this effect

Thank so much

[vincenzopalazzo]

Resolved, this is my fault because I had two files different bootstrap include inside the file Html