<p dir="auto">Here is a link that you can experiment with the problem.<br>
<a href="https://dl.dropboxusercontent.com/u/15234/bs3/index.html" rel="nofollow">https://dl.dropboxusercontent.com/u/15234/bs3/index.html</a></p>
<p dir="auto">Steps to reproduce:</p>
<ol dir="auto">
<li>Reduce the size until navbar collapses</li>
<li>Click on toggle button</li>
<li>Click on dropdown</li>
<li>While expanded, increase the width until the navbar collapses</li>
<li>Bug!</li>
</ol>
<p dir="auto"><a target="_blank" rel="noopener noreferrer nofollow" href="https://camo.githubusercontent.com/cb30702a71325ea14a339dc68a62f1e22ca835b0290937250864b595df65ddc6/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f3132353637362f3936343837322f34373531343636382d303531662d313165332d393466392d3633326530373739633535362e706e67"><img src="https://camo.githubusercontent.com/cb30702a71325ea14a339dc68a62f1e22ca835b0290937250864b595df65ddc6/68747470733a2f2f662e636c6f75642e6769746875622e636f6d2f6173736574732f3132353637362f3936343837322f34373531343636382d303531662d313165332d393466392d3633326530373739633535362e706e67" alt="screen shot 2013-08-14 at 10 18 25 pm" data-canonical-src="https://f.cloud.github.com/assets/125676/964872/47514668-051f-11e3-94f9-632e0779c556.png" style="max-width: 100%;"></a></p>
<p dir="auto">Scrollbars show for the y-overflow when moving from collapse to full width and a dropdown is open in the navbar.</p>
<p dir="auto">To reproduce, shrink the browser window down to where the nav collapses and then open a dropdown causing the nav to overflow and show the scroll bar. Then, resize back to full width without first closing the nav. Because the <code class="notranslate">collapse</code> class is no longer on the <code class="notranslate">navbar-collapse</code> div, the navbar shows the scrollbars because its overflow-y is set to auto;</p>
<p dir="auto">I was seeing this while using latest version of Chrome on Windows. Haven't looked in other browsers.</p>
<p dir="auto">The following LESS Fixes the issue:</p>
<div class="snippet-clipboard-content notranslate position-relative overflow-auto" data-snippet-clipboard-copy-content="@media screen and (min-width: @grid-float-breakpoint) {
    .navbar-collapse {
        overflow: visible !important;
    }
}"><pre class="notranslate"><code class="notranslate">@media screen and (min-width: @grid-float-breakpoint) {
    .navbar-collapse {
        overflow: visible !important;
    }
}
</code></pre></div>