OK. More info on this. If I disable the Facebook and Twitter meta data in WordPress SEO by Yoast, The problem is resolved.
Here is a sample of the source code:
<!DOCTYPE html>
<html lang="en-US" prefix="og: https://ogp.me/ns#">
<head>
<script type='text/javascript'>var ct_ajaxurl='https://www.athlavard.com/wp/wp-admin/admin-ajax.php';</script>
<meta charset="UTF-8"/>
<title>Forum - AthCraft.com</title>
<meta name="viewport" content="width=device-width, initial-scale=1"/>
<script type='text/javascript'>//<![CDATA[
var sp_platform_vars={"focus":"forum","mobile":"0","device":"desktop","tooltips":"1","mobiletheme":"0","checkboxes":"","headpadding":"0","saveprocess":0,"checkiframe":"no",};
//]]></script>
<script type='text/javascript'>var ct_ajaxurl='https://www.athlavard.com/wp/wp-admin/admin-ajax.php';</script>
<!-- This site is optimized with the Yoast WordPress SEO plugin v2.1.1 - https://yoast.com/wordpress/plugins/seo/ -->
<!-- Admin only notice: this page doesn't show a meta description because it doesn't have one, either write it for this page specifically or go into the SEO -> Titles menu and set up a template. -->
<meta property="og:locale" content="en_US"/>
<meta property="og:type" content="article"/>
<meta property="og:title" content="Forum - AthCraft.com"/>
<div id="dialogcontainer" style="display:none;"></div><noscript><div><pre><code>This forum requires Javascript to be enabled for posting content</code></pre></div></noscript>
<a id="spForumTop"></a>
<!-- Simple:Press display start -->
<div id="spMainContainer"><div id='spMobilePanel'></div><div class='spHeadContainer'>
<div style='clear: both; height:1px;'></div>
<div class='spPlainSection'>
Notice that output starts before the head tag closes.
As, I mentioned, when I disable the OG and Twitter meta, this does not happen.
Thanks!