"back" button in browsers not functioning in Qusq template

Hello,
HELP! When navigating this template, the back button in the browser is displaying the background color of the page ONLY. No page content whatsoever. The address bar is showing that it is going back to the page when you click it, but there’s no content. If I hit refresh, the page will load correctly.

I uploaded your template and tested it with the clean unaltered version, so I know it’s not something I have modified. It is working in Chrome, but not Safari or Firefox.

Click here, https://moving-pixels.com/dist/index.html
…then click the macintosh communications logo image, then hit the back button in Firefox or Safari and the home page will display the background color only.

This is happening in: Safari 10 and Firefox 48.0.1

Thanks, Gina