As the database was corrupt, that is the most likely reason. The navigation uses some information from the database and some from the book as you are reading.
You can also get some strange behaviour if you replace a book without deleting it first. It is safe if the structure of the book doesn't changed. Changing spelling, styles etc is safe. But changing the ToC or the internal file structure can lead to some strange behaviour.
It could also be an error in the book. If it doesn't work after the sign out/in, this will be the problem.
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