Textures: (I have tested each texture and model individually)
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Items:
/give @s minecraft:writable_book{CustomModelData:1}/give @s minecraft:written_book{CustomModelData:1}Here is a video to better display what is meant. When signing the writable book the CustomModelData NBT data is not transferred to the created written book.
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Environment
Microsoft Windows Version 1809 (17763.104)
Java version "1.8.0_171"
Java(TM) SE Runtime Environment (build 1.8.0_171-b11)
Java HotSpot(TM) 64-Bit Server VM (build 25.171-b11, mixed mode)
This issue relates to MC-138892.