Well, this is odd. The two links I originally posted, to two different passages where this error was occurring (sections 09 and 14 of the book "Et si c'était vrai"), now lead to two identical copies of the second passage, section 14. Or rather, I guess the text content of section 09 has now been overwritten with the text content from section 14? If you open both links, you'll see that, although one is labeled as section 09 and one as section 14, they are identical in terms of content (they both start with "Il la vit de loin"). This was not originally the case when I uploaded them.
In any case, there is also good – if confusing – news. When I opened the link to section 09, I saw the original "weird word", "luurankosi", appearing as the very first word in the passage. It was immediately followed by all the text that makes up the content of section 14, including the word "Admata". But when I went to edit the passage, I was able to delete the word "activerait" from the very beginning of the passage (appearing as "luurankosi"), and also deleted an extra space that hadn't been there before from after the word "déroutante" (appearing as "Admata") – and when I hit save and opened the passage again, both "luurankosi" and "Admata" were gone. And "déroutante" does appear correctly, exactly where it's supposed to be! Yay!
I can't check if the first passage (section 09, the one that's supposed to contain the word "activerait") is fixed, because that passage has been overwritten with the content of section 14. But this does seem to suggest that the problem has been fixed, even if something a little odd happened along the way. (It's no big deal to "lose" a section – I'd already finished reading that book anyway.)
Thanks very much for the help, Leo!