Did you ever figure out where the bad text anchor was? I have the same error when exporting an epub file, however my InDesign document does not contain a TOC, nor does it contain any links to images or text shown in the path listed in the error. Also notable is that the export to epub process did create a file, but it won't open in Adobe Digital Editions. There were no other errors when I generated the epub file so I am really confused. I am hoping someone out there can help figure out how to find the text anchor. I am stumped.
Hello SueCampbell54, I was facing the same problem (and frustration) and this is what I found. In my document, there were hyperlinks to websites that didn't exist. As we know that InDesign checks the integrity of the hyperlinked web addresses, this feature is what led to the generation of the "External Text Anchor not found: 3" error.
I removed those hyperlinks and the error disappeared when I exported the file to epub again. Hope this helps.