Written Book with custom actions no longer work if they are too long.

Did you get the book before upgrading to 1.20.4, where it previously worked, and then after upgrading it did it break? Or did you use a command in 1.20.4 that used to work before, and that new book did not work correctly?

In either case, please provide the full command used to get that book.

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Did you get the book before upgrading to 1.20.4, where it previously worked, and then after upgrading it did it break? Or did you use a command in 1.20.4 that used to work before, and that new book did not work correctly?

Both, actually. The command's VERY long so here's a shortened version which has the same issue:

/give @p written_book{pages:['["",{"text":"Demonstration
n","color":"light_purple","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"ClickThis","underlined":true,"color":"light_purple","clickEvent":{"action":"run_command","value":"/tp @s 1421 68 -2308"},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"\\n
n","color":"reset","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"Defense","underlined":true,"color":"dark_blue","clickEvent":{"action":"change_page","value":2},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"\\n
n","color":"reset","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"Offense","underlined":true,"color":"dark_blue","clickEvent":{"action":"change_page","value":3},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"\\n
n","underlined":true,"color":"dark_blue","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"Potions","underlined":true,"color":"dark_blue","clickEvent":{"action":"change_page","value":4},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"\\n
n","color":"reset","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"Blocks","underlined":true,"color":"dark_blue","clickEvent":{"action":"change_page","value":5},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"\\n
n","underlined":true,"color":"dark_blue","hoverEvent":{"action":"show_text","contents":"Stuff lol"}},{"text":"Strategies","underlined":true,"color":"dark_blue","clickEvent":{"action":"change_page","value":6},"hoverEvent":{"action":"show_text","contents":"Stuff lol"}}]'],title:"PVP Kit Book",author:"https://minecraft.tools/en/book.php",display:{Lore:["A Book With All Your PVP Needs!"]}}

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We're tracking this issue in MC-267619, so this ticket is being resolved and linked as a duplicate.

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Quick Links:
📓 Bug Tracker Guidelines – 💬 Community Support – 📧 Mojang Support (Technical Issues) – 📧 Microsoft Support (Account Issues)
📓 Project Summary – ✍️ Feedback and Suggestions – 📖 Game Wiki