SSIS Package - Error Exporting Data to Flat File - Invalid Character
You have to deal with the unicode replacement character by calling it what it is:

Row.Description = Row.Description.Replace(NCHAR(65533), "a")


EDIT:

I apologize as I first gave you a pseudo-SQL Server solution, but with some additional research learned that SSIS behaves a little differently. I'm linking my source that gives multiple solutions, and for an answer will include the first. It seems that you could add a derived column component that would allow you to add a new column (e.g. strDescription from your table using the Type Cast operator DT_STR which will convert the unicode to string. You should then be able to use this derived column in place of the original column in you CSV destination. source Hope that helps!