It's possible to create a book, but when you click on it the error "connection to server edit.php has failed" emerges.

Interestingly, this only happens if a book has no chapters. If a book has already chapters, e.g. when you upload a course with already existing books from a different server with a different moodle version (lower than 4.0), you can click on the book. However, when you try to save any changes, e.g. change order of chapters, change the content, the error occurs again.

This bug only happens in 4.x. No issues with lower versions.

We run our moodle on NGINX.

We didn't install any plugins besides of 2factor-auth.:

• https://moodle.org/plugins/auth_a2fa
• https://moodle.org/plugins/profilefield_afaqr