Text Formatting Bug

Hey Minecraft Dev Team. I am trying to add some custom formatting into Books in Minecraft and there seems to be a bug with the game and how it is interpreting the formatting codes. It shows fine in the preview window of the book and quill but after signing it a bunch of ####### show up and replace some of the text. Please see attached video. Thank you!

Video of Bug:
https://drive.google.com/file/d/1uN1codLvgWpYOqKfNg7cNPKnUDxRGrkN/view?usp=sharing