As soon as the page loads, we start loading the next one. Browsers often stop loading resources when this happens, so I think that's what it was doing here. This display may have been down to the exact way the packets came down the wire as I didn't see it like this, but I did see it not load the sidebar. I've adjusted the JS to ever so slightly delay when it starts loading the next one so that all the HTML should be transferred and shown. It made it show correctly in my tests.