Plugin Changes Site Taxonomy

I should have read these comments before I installed this plugin. I had a tree previously in place that starts with /books. I suppose that this plugin uses the same root I believe for now after I realized that all pages above the books were NOT FOUND, I deactivated the plugin and deleted it. Then I went to the pages, which are all still there (no content was erased), and saved them again. The result is now that these links like /books/en, /books/de, or /books/fr end up in a loop back to the homepage. However, the end of the link chain, the individual book links, have not been affected. I will try now to reinstall the plugin and see what I can change in the setup. If I cannot do what needs to be done and their support doesn’t reply, there is only one solution that is very awkward. I would have to rename the root of all books to /publications. I believe this will solve the problem, but everywhere on the Internet I have propagated my books with the links to /books, etc. Such a thing should never happen!!!! These guys have to be pulled out of the WordPress developer community, for this is simply a totally amateurish mistake.