The problem occurs if you have a Link and the text content has a break-line; when you navigate through tab selection, normally the text is selected, the selection for those cases, the reader locates the selection in the wrong place, it depends on the resolution or the scale of the window, at more resolution, the selection place is worse.

Example of the FO structure used for a link with break-line is as follows:

      <fo:block space-before="0pt" start-indent="0.63in" space-after="9pt">The Quick Response
        (QR) code images in some parts of this guide provide links to additional video
        explanations of particular topics. For example, you can find examples of such images in
          <fo:basic-link axf:pdftag="''" internal-destination="unique_14"><fo:inline
            axf:pdftag="Link" color="rgb(71,89,245)" text-decoration="underline"
                ><fo:inline><fo:inline>Customer Self-Repair parts</fo:inline> on page
                <fo:page-number-citation ref-id="unique_14"
          /></fo:inline></fo:inline></fo:basic-link>.</fo:block>

Open the pdf output.
Go and click content from the first page.
Press the Tab Key from your Keyboard.
Continue pressing the Tab Key to see how the text from links are selected (if the link doesn't have a break-line the selection is correct, but with break-line the selection is wrong located)
Increase the resolution of the text, the tab selection change over the document content.
Thanks.