Kindle oasis rendering puctiation strangely

I bought a Kindle Oasis for my wife, which arrived this morning from Amazon. We loaded some of her massive collection of e-books. On the book she is currently reading, punctuation, such as quotations marks, are rendered as a square with two zeros, and two numbers, usually 92, 93, or 94, below the two zeros. Does anyone know what causes this and if there is a fix for this?