I would say it needs to be a search and replace method to cleanse the file since you can't pinpoint where the problem has arisen from.

If the source was typed in English using a text editor then the characters MIGHT have been a datatype conversion issue but since you are getting hazy on the actual origin so just bite the bullet and do the find and replace. Its a one off effort if you are now authoring in Word.

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Andrew Lockton
Chrysalis Design, Melbourne Australia