So, whenever I finish writing in a book & quill and decide to sign it with a title, the whole text is gone and the book is just blank. Apparently this has happened to others according to some of the Discord and Reddit members.

Whenever you write in a book and decide to finish it by signing it and giving the book a title, and then decide to reopen it on Bedrock edition there is nothing there; it's just a blank book even on lecterns.