Before Continuing:

• Check you are using the latest version of the mods and its dependencies
• Always include a latest.log if you are crashing
• Remove known hacky mods such as: Optifine, Fabric API/Connector on forge, and every kind of hybrid server like Mohist and Velocity. None of these are supported. Also try without other lesser usual suspects like Sodium and Lithium.
• If you are unsure which mod is the culprit.
  Disable all of your mods and enable them 1-2 mods each time to isolate the culprit
• Confirm that there is no existing issue with a similar description submitted in the list of issues.

Version

1.21.1-NEOFORGE

Supplementaries Version

supplementaries-1.21-3.3.5-neoforge

Moonlight Lib Version

moonlight-1.21-2.19.5-neoforge

Describe Issue

After placing books in the world, trying to remove one of them individually (with shift + rightclick) instead causes the placed books to both start becoming invisible and/or the amount of shown books starts showing a lower amount, despite the player not (necessarily) getting any actual book back. When the stack is broken, not all books will be present.

E.g. place 4 books in one block, shift + RMB to take 1 or a couple, not obtain any books into inventory, while breaking the remaining stack might give 3 instead of 4 (even when trying to take multiple), or less. It's fairly vague in how many less there will be, but very consistent in that it deletes books - they won't be in the placed stack anymore (even when broken), nor in player's inventory, nor on the ground, even after reloading the world/game.

I'm not sure if the shift + RMB shortcut is even meant to be an intended way to take individual books, but it's a key combo that seems to come natural to people to try and thus if it's not intended to work, at least it should not be deleting books.

Could reproduce in a clean NeoForge 1.21.1 instance with no other mods present (just supplementaries-1.21-3.3.5-neoforge + moonlight-1.21-2.19.5-neoforge), tried it with first release candidate of the mod too (so supplementaries-1.21-3.1.0-neoforge + moonlight-1.21-2.18.2-neoforge + create-1.21.1-6.0.0) to confirm the issue is not something relatively new, and even could reproduce in a clean Fabric 1.21.1 install (so with supplementaries-1.21-3.3.5-fabric + moonlight-1.21-2.19.5-fabric + fabric-api-0.116.4+1.21.1).

I also made a bug report in the Discord server #bugs-and-issues channel in case you prefer that, I linked the two issue posts to each other for convenience, here's the post in discord: https://discord.com/channels/790151253144895508/1393690303197745153/1393690303197745153

Quick video demonstration:

In addition, once such a stack has been shift + rightclicked, it seems to just be generally a broken stack where you can keep placing books infinitely into, all which will be gone forever.

In the NeoForge 1.21.1 setup, when two stacks are next to each other and one or both enter this bugged state, the books also occasionally turn into large texture error blocks (with purple/black checkerboard pattern) - I could not reproduce this in the Fabric setup but could consistently with NeoForge.

Additional footage of the infinite black hole such a bugged stack can represent (happens both in Fabric and NeoForge) and the possible texture error in NeoForge:

I'm having same issue i was about to report it, glad i searched to find someone else already did, i hope the issue get fixed soon as i use bookshelves feature quite a lot for my library (i would be devastated if any of them get removed as all of them are written books), i usually just break the pile with left click to be safe