<p>Ok, I think I know what's going on here:</p>
<p>The following code triggers the asynchronous request to fetch changeset details:</p>
<div class="highlight highlight-source-js"><pre>    <span class="pl-smi">$</span>.<span class="pl-en">ajax</span>({
      url<span class="pl-k">:</span> <span class="pl-c1">window</span>.<span class="pl-c1">location</span>.<span class="pl-c1">pathname</span>,
      method<span class="pl-k">:</span> <span class="pl-s"><span class="pl-pds">"</span>GET<span class="pl-pds">"</span></span>,
      data<span class="pl-k">:</span> data,
      <span class="pl-en">success</span><span class="pl-k">:</span> <span class="pl-k">function</span> (<span class="pl-smi">html</span>) {
        <span class="pl-en">$</span>(<span class="pl-s"><span class="pl-pds">"</span>#sidebar_content .changesets<span class="pl-pds">"</span></span>).<span class="pl-en">html</span>(html);
        <span class="pl-en">updateMap</span>();
      }
    });</pre></div>
<p>Upon success we call updateMap()</p>
<div class="highlight highlight-source-js"><pre>  <span class="pl-k">function</span> <span class="pl-en">updateMap</span>() {
    changesets <span class="pl-k">=</span> <span class="pl-en">$</span>(<span class="pl-s"><span class="pl-pds">"</span>[data-changeset]<span class="pl-pds">"</span></span>).<span class="pl-en">map</span>(<span class="pl-k">function</span> (<span class="pl-smi">index</span>, <span class="pl-smi">element</span>) {
      <span class="pl-k">return</span> <span class="pl-en">$</span>(element).<span class="pl-c1">data</span>(<span class="pl-s"><span class="pl-pds">"</span>changeset<span class="pl-pds">"</span></span>);
    }).<span class="pl-c1">get</span>().<span class="pl-en">filter</span>(<span class="pl-k">function</span> (<span class="pl-smi">changeset</span>) {
      <span class="pl-k">return</span> <span class="pl-smi">changeset</span>.<span class="pl-smi">bbox</span>;
    });

    <span class="pl-en">updateBounds</span>();

    <span class="pl-k">if</span> (<span class="pl-c1">window</span>.<span class="pl-c1">location</span>.<span class="pl-c1">pathname</span> <span class="pl-k">!==</span> <span class="pl-s"><span class="pl-pds">"</span>/history<span class="pl-pds">"</span></span>) {
      <span class="pl-k">var</span> bounds <span class="pl-k">=</span> <span class="pl-smi">group</span>.<span class="pl-en">getBounds</span>();
      <span class="pl-k">if</span> (<span class="pl-smi">bounds</span>.<span class="pl-en">isValid</span>()) <span class="pl-smi">map</span>.<span class="pl-en">fitBounds</span>(bounds);
    }
  }</pre></div>
<p>This issue is caused by <code>window.location.pathname !== "/history"</code>: when closing the sidebar before the request finishes, the URL is no longer /history, but /#map. As a consequence we inadvertently set some new bounds.</p>

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