When Etlworks flow creates a CSV file, by default, the information about the column's data types in the source database is getting lost. So if another flow reads the same file it assigns the data types to the columns by sampling the data, which is not always 100% accurate.
If you want to preserve the exact data types simply enable the option Save Metadata for the source and the destination CSV formats. If this option is enabled the system will store column names and data types in the XML file with the same name and in the same location as the original CSV file.
When to enable this option
Generally speaking, it makes sense to enable this option if the CSV file is created by the Etlworks flow that extracts data from a database and then used by another Etlworks flow to load data into a different database.