Anchor hyperlinks inserted in a Rich Text field might be resolved with a duplicated href attribute value. For example:
<a href="#A">Text</a>
is rendered as:
<a href="#A##A" "="">Text</a>
To resolve the issue, consider one of the following options:
<processor type="Sitecore.Pipelines.RenderField.SetAnchorsPositionInLinks, Sitecore.Kernel" />