Thanks for your quick response!
Yes, everything looks fine when I open the file in Calibre, not showing any symbol issues whatsoever. It's only when it gets transferred onto the tablet. I also have not encountered this issue with any other e-books that I have so far put onto my tablet. I've so far attempted to convert using several other character encoding like cp1252 and utf-8, but have had no luck. I've done this by converting the file and then transferring that converted file to the tablet. The square symbol is primarily replacing quotes, but also commas and hyphens.