Headings going awry

I am trying to convert a number of Microsoft Word documents (.doc or .docx files) to e-books. I have tried saving the documents as .RTF files, and also as "filtered HTML" files. With either format, converting to EPUB (using Calibre 0.8.45) generates a readable file, but with significant errors.

The errors seem to be related to changes that are applied to the major headings. In the original HTML file, a heading looks like:

<h1><a name="_Toc244191671"></a>New York Bumper Stickers</h1>

However, in the HTML file in the Debug\Parsed folder, the heading has been changed to:

<h1><a name="&lt;i&gt;Toc244191671”&gt;&lt;/a&gt;New York Bumper Stickers&lt;/h1&gt;

As a result:

• The paragraphs that follow the <h1> are appearing in the large font of the <h1>
• The reference from the <a> is appearing as text
• The text of the <h1> is not visible

In other cases, a very similar heading changes from:

<h1><a name="_Toc244191667"></a><a name="_Toc104266959">You know you’re from </a>Jersey when …</h1>

to:

<h1 style="margin-top:1em;margin-bottom:1em;"><a name="&lt;i&gt;Toc244191667”&gt;&lt;/a&gt;&lt;a name=">Toc104266959”&gt;You know you’re from </a>Jersey when …</h1>

In this case, the text of the anchor is visible, but, because the </h1> is not corrupted, the subsequent text is properly formatted.

Can anybody tell me why some of the HTML tags are being corrupted? Also, why is the text:

&lt;i&gt;

being inserted before the text of the anchor name attribute?