When opening the Manual-Book the World gets "Transparent", like in noclip, i can see ores laying under the surface.

After closing the book it gets back to normal, see the images.

Minecraft 1.12
Forge 14.21.1.2406

Bug:
http://imgur.com/CC9fFg2

Normal:
http://imgur.com/osV0wUA

UPDATE
It seems that this only happens if there are animated recipes on the pages

I can't reproduce it with just ID+IT+CC(+ComCap) installed.
Can you try do reproduce it with just these mods on your end?

It could be another mod hooking into item rendering and forgetting to reset some rendering flags.

Hi,
with just these mods there is no issue, so its another mod i guess.

Ok, my suggestion is to add/remove mods until you find the one that causes the issue, and report it to their issue tracker.
That mod will likely cause other related rendering issues as well.