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Yes. It's a new feature (implemented in v19.2 or v19.5) supporting a form of accessiblity that is not fully cooked yet and is not universally implemented; Kindle simply strips it out, but many other EPUB vendors see the code it adds as a flaw. Don't check it, ever, until and unless you understand the accessibility it enables, need that feature, and the vendors have slowly caught up to the new standards and features.
Also stay out of the Accessiblity menu (a submenu of the Metadata export pane)
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The issue is very likely in the pagelist. If you check "Page Navigation" on EPUB export, InDesign with put markers where the page breaks occur in the text. There is a minor bug where it sometimes lists a page number twice and then iterates the ID in the second instance: <span epub:type="pagebreak" role="doc-pagebreak" id="page123-1" aria-label=" Page 123. " />. The error will point to the line in toc.xhtml where that occurs and then you can hunt down and delete that erroneous pagebreak.