The last normally working version was 1.21.8. Both versions 1.21.10 and 1.21.11 fail to work properly.

Issue: After performing operations on the ChiseledBookshelfInventory(e.g., inventory.clear(), inventory.setItem(0, null)), the client does not update its state. It appears as if the items have not been cleared, but players cannot take them out. Using the vanilla /data get block command confirms the bookshelf is empty server-side. However, this issue persists even if the player reconnects to the server or if the server is restarted.

Workaround: Placing a new book into the CHISELED_BOOKSHELFcauses it to update to the correct state.

ChiseledBookshelf bookshelf = (ChiseledBookshelf) block.getState();
ChiseledBookshelfInventory inventory = bookshelf.getInventory();

inventory.clear();