Hi,
Thank you very much for the details, it helps me a lot!
The results are very likely matched from either the selected custom fields or via the taxonomy terms as configured here: https://i.imgur.com/FLwTr7O.png
There is probably a custom field or a category name associated with those results which makes it a match. Try removing some custom fields or turning off the taxonomy search to see if that makes a difference, it should resolve the issue.
I also tried the search when logged in, but it seems to work okay on my end: https://i.imgur.com/sqx56vp.png
You may only need to clear the browser cache, that should resolve that issue.
