admin theme selector bug

When I duplicate one of the existing default themes by making a copy of and re-naming the folder, my page does not display the additional available themes correctly. Here is a snippet of the html straight from the browser view of the admin theme selector page.

If you copy this to a text editor for easy reading, you can see that in the second theme somehow the <h3> tag is not closing until after most of the theme’s description instead of after the title in the heading of the style.css which comes from an exact duplicate of the style.css file of the first theme listed below.

In other words, they should display identically, but there is something wrong. This happens whether I make a copy of an existing template, or create my own from scratch. Please help!

Thanks, Paul

<div class="wrap">

    <h2>Current Theme</h2>

		<div id="currenttheme">
			<h3> by </h3>
			<p></p>
			<p>All of this theme’s files are located in <code></code>.</p>
		</div>

    <h2>Available Themes</h2>

		<div class="available-theme">

			<h3><a href="themes.php?action=activate&template=classic&stylesheet=classic&_wpnonce=561f750d50">WordPress Classic</a></h3>

			<a href="themes.php?action=activate&template=classic&stylesheet=classic&_wpnonce=561f750d50" class="screenshot"><img src="https://localhost/screenshot.png" alt="" /></a>

			<p>The original WordPress theme that graced versions 1.2.x and prior.</p>
			<p>Tags: mantle color, variable width, two columns, widgets</p>

		</div>

		<div class="available-theme">

			<h3><a href="themes.php?action=activate&template=default&stylesheet=default&_wpnonce=72c300eb8d">WordPress Classic Theme URI: https://www.ads-software.com/ Description: The original WordPress
					theme that graced versions 1.2.x and prior. Version: 1.5 Author: Dave Shea Tags: mantle color, variable width, two columns, widgets Default WordPress by Dave Shea || https://mezzoblue.com
					Modifications by Matthew Mullenweg || https://photomatt.net This is just a basic layout, with only the bare minimum defined. Please tweak this and make it your own. :) */</a></h3>

			<a href="themes.php?action=activate&template=default&stylesheet=default&_wpnonce=72c300eb8d" class="screenshot"><img src="https://localhost/screenshot.png" alt="" /></a>

			<p>The original WordPress theme that graced versions 1.2.x and prior. Version: 1.5 Author: Dave Shea Tags: mantle color, variable width, two columns, widgets Default WordPress by Dave Shea || https://mezzoblue.com
				Modifications by Matthew Mullenweg || https://photomatt.net This is just a basic layout, with only the bare minimum defined. Please tweak this and make it your own. :) */</p>
			<p>Tags: mantle color, variable width, two columns, widgets Default WordPress by Dave Shea || https://mezzoblue.com Modifications by Matthew Mullenweg || https://photomatt.net This is just a basic
				layout, with only the bare minimum defined. Please tweak this and make it your own. :) */</p>

		</div>

    <h2>Get More Themes </h2>

		<p>You can find additional themes for your site in the <a href="https://www.ads-software.com/extend/themes/">WordPress theme directory</a>. To install a theme you generally just need to upload the theme folder
			into your <code>wp-content/themes</code> directory. Once a theme is uploaded, you should see it on this page. </p>

</div>