The Bug

If you put a command-generated book on a lectern and click on a text section that has the change_page clickevent, even though the page appears to change, the redstone signal strength coming from the comparator does not update. 

How to Reproduce

1. Create a book using the change_page clickevent via https://mcstacker.net/1.14.php or get a pre-made book by downloading this datapack. https://www.planetminecraft.com/mod/armor-stand-customizer-v2-0-1-14/ If you chose the latter option, you can get the book by typing  /function cvt_armorstand:guide, placing an armor stand and dropping a book on it, or clicking on the tellraw after typing /reload. 
2. Place the book on the lectern, open it, and then click the text with the change_page clickevent. 
3. Notice how the page number and redstone signal strength doesn't match.