I have this navbar - everything works just fine, but one thing is wrong - on the mobile, when you see the navbar-toggler icon - you click it - navbar drops down and shows, but when you click again - no response. You need to click at least twice, sometimes more to close the dropdown menu again. Where is the issue? Thanks

```
<section id="nav">
<nav class="navbar navbar-expand-md navbar-light bg-dnsa sticky-top">
<div class="container padding">
    <a class="navbar-brand logo" href="index.html"><img src="img/logo.png" class="logoo"></a>
    <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarNavDropdown" aria-controls="navbarNavDropdown" aria-expanded="false" aria-label="Toggle navigation">
<span class="navbar-toggler-icon"></span>
    </button>
    <div class="collapse navbar-collapse" id="navbarNavDropdown">
       <ul class="navbar-nav ml-auto">
          <li class="nav-item">
             <a class="nav-link" href="#">O nás</a>
          </li>
          <li class="nav-item">
             <a class="nav-link" href="#">DAS"DAL</a>
          </li>
          <li class="nav-item">
             <a class="nav-link" href="#">Formulář pro objednávku</a>
          </li>
          <li class="nav-item">
             <a class="nav-link" href="#">Kontakt</a>
          </li>
       </ul>
    </div>
  </div>
 </nav>
 </section>

```