Please update to last version of our Joomla Book library
If this not help:Could you give to us
full FTP and supper admin access
and our team will find solution special for You, FTP and admin access You can send to our contact form.
Link to website.
Detail description: How reproduce error. Step by step. Detail description: how we may reproduce this.
Site Super Admin:
P.S. Please do site backup 2 times per month this help to you forecast and fix very many errors