The values are just read from the datareader and into the fields, so there's no conversion going on in our code: the string provided by the datareader on the firebird database is placed inside the field.
Could you create a small .NET console app with normal ADO.NET classes, like FbDataReader and FbConnection to create a small datareader on that table with a SQL query to fetch that particular row and with that connection string? Please check if reader.GetValues() in that case produces a string which does contain the right values.
(and please next time post in a forum which is actually monitored. Thanks).