Moodle in English

hi,

I use moodle 3.5 with admin access.

i created a new chapter to my book, its id is 10 and it is 1rst position in the TOC.

When i visit the page (unlog) , i got an error :

https://www.monsite.fr/mod/book/view.php?id=402&chapterid=10

This is strange because others chapter and the root book are accessible !

https://www.monsite.fr/mod/book/view.php?id=402
https://www.monsite.fr/mod/book/view.php?id=402&chapterid=9
https://www.monsite.fr/mod/book/view.php?id=402&chapterid=8

..etc

but the 10th chapter got a bug!
as admin, i tried to clean the content, change its position, save, re-save but it did not solve the problem.

what is the strange bug ou missing part ?

And by the way, the documentation page is missing :

http://docs.moodle.org/35/en/error/mod_book/errorchapter

error/mod book/errorchapter