title: Bootstrap 4: Dropdown in card breaks across columns?
body: <p>I have a problem using bootstrap 4 (specifically, reactstrap but I can recreate the same issue in bootstrap) where I am using 'card-columns' to create a grid of cards, each card having a dropdown menu in the 'card-footer'.
  The problem is that once I have 4 or more cards the dropdown appears to break across columns somehow....where it is rendered is different to where chrome highlights the element, as shown by this image:</p>
  
  <p><a href="https://i.stack.imgur.com/v96bk.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/v96bk.png" alt="enter image description here"></a></p>
  
  <p>If I increase my card count, then on some cards when I open the dropdown, the card will change position - they 'jump around'.</p>
  
  <p>Minimal example:</p>
  
  <p><div class="snippet" data-lang="js" data-hide="false" data-console="true" data-babel="false">
  <div class="snippet-code">
  <pre class="snippet-code-css lang-css prettyprint-override"><code>body {
    margin: 10px;
  }
  
  .dropdown-menu {
    margin-top: 10px;
    margin-bottom: 10px;
  }</code></pre>
  <pre class="snippet-code-html lang-html prettyprint-override"><code>&lt;script src="https://code.jquery.com/jquery-3.2.1.slim.min.js" integrity="sha384-KJ3o2DKtIkvYIK3UENzmM7KCkRr/rE9/Qpg6aAZGJwFDMVNA/GpGFF93hXpG5KkN" crossorigin="anonymous"&gt;&lt;/script&gt;
  &lt;script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.12.9/umd/popper.min.js" integrity="sha384-ApNbgh9B+Y1QKtv3Rn7W3mgPxhU9K/ScQsAP7hUibX39j7fakFPskvXusvfa0b4Q" crossorigin="anonymous"&gt;&lt;/script&gt;
  &lt;script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/js/bootstrap.min.js" integrity="sha384-JZR6Spejh4U02d8jOt6vLEHfe/JQGiRRSQQxSfFWpi1MquVdAyjUar5+76PVCmYl" crossorigin="anonymous"&gt;&lt;/script&gt;
  &lt;link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0/css/bootstrap.min.css" integrity="sha384-Gn5384xqQ1aoWXA+058RXPxPg6fy4IWvTNh0E263XmFcJlSAwiGgFAW/dAiS6JXm" crossorigin="anonymous"&gt;
  
  
  &lt;div class="container-fluid h-100"&gt;
    &lt;div class="mx-4 my-2 row"&gt;
      &lt;div class="mx-4 row"&gt;
        &lt;div class="card-columns"&gt;
          &lt;div class="card border-secondary"&gt;
            &lt;div class="card-footer"&gt;
              &lt;div class="row"&gt;
                &lt;div class="col-md-8"&gt;
                  &lt;div class="btn-group show"&gt;
                    &lt;button class="dropdown-toggle btn btn-outline-secondary"&gt;
                     More
                    &lt;/button&gt;
                  &lt;/div&gt;
                &lt;/div&gt;
              &lt;/div&gt;
            &lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="card border-secondary"&gt;
            &lt;div class="card-footer"&gt;
              &lt;div class="row"&gt;
                &lt;div class="col-md-8"&gt;
                  &lt;div class="btn-group show"&gt;
                    &lt;button class="dropdown-toggle btn btn-outline-secondary"&gt;
                     More
                  &lt;/button&gt;
                  &lt;/div&gt;
                &lt;/div&gt;
              &lt;/div&gt;
            &lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="card border-secondary"&gt;
            &lt;div class="card-footer"&gt;
              &lt;div class="row"&gt;
                &lt;div class="col-md-8"&gt;
                  &lt;div class="btn-group show"&gt;
                    &lt;button class="dropdown-toggle btn btn-outline-secondary"&gt;
                     More
                  &lt;/button&gt;
                  &lt;/div&gt;
                &lt;/div&gt;
              &lt;/div&gt;
            &lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="card border-secondary"&gt;
            &lt;div class="card-footer"&gt;
              &lt;div class="row"&gt;
                &lt;div class="col-md-8"&gt;
                  &lt;div class="btn-group show"&gt;
                    &lt;button class="dropdown-toggle btn btn-outline-secondary"&gt;
                     More
                  &lt;/button&gt;
                    &lt;div role="menu" class="dropdown-menu show" x-placement="bottom-start" style="position: absolute; will-change: transform; top: 0px; left: 0px; transform: translate3d(0px, 27px, 0px);" data-placement="bottom-start"&gt;
                      &lt;button class="dropdown-item"&gt;
                        Button 1
                      &lt;/button&gt;
                      &lt;button class="dropdown-item"&gt;
                        Button 2
                      &lt;/button&gt;
                      &lt;button class="dropdown-item"&gt;
                        Button 3
                      &lt;/button&gt;
                    &lt;/div&gt;
                  &lt;/div&gt;
                &lt;/div&gt;
              &lt;/div&gt;
            &lt;/div&gt;
          &lt;/div&gt;
          &lt;div class="card border-secondary"&gt;
            &lt;div class="card-footer"&gt;
              &lt;div class="row"&gt;
                &lt;div class="col-md-8"&gt;
                  &lt;div class="btn-group show"&gt;
                    &lt;button class="dropdown-toggle btn btn-outline-secondary"&gt;
                     More
                  &lt;/button&gt;
                  &lt;/div&gt;
                &lt;/div&gt;
              &lt;/div&gt;
            &lt;/div&gt;
          &lt;/div&gt;
        &lt;/div&gt;
      &lt;/div&gt;
    &lt;/div&gt;
  &lt;/div&gt;</code></pre>
  </div>
  </div>
  </p>
  
  <p>In this example, only the last 2 buttons of the menu seem to 'break' and appear elsewhere - your screen needs to be wide enough to show more than 1 column for the problem to occur. </p>
  
  <p>I imagine the problem is to do with the dropdown extending beyond the cards' boundaries when opened, even though it is absolutely positioned.</p>
  
  <p>How can I make such a dropdown without it interfering with the card-columns layout?</p>