Are you using MySQL? If so, it's possible that you were hitting the problem described here: Unexpected character in found when decoding object value
Since this is likely a truncated entry in the database, going via Prodigy likely won't work because it won't be able to load the dataset (which is why you see the error here). So the best solution would be to just do it manually in your database – either with an SQL query, or by using a database browser.