Can you state what versions of the IBM i operating system you are on, and what version of Client access?
You say you are using the Data transfer facility, so this creates a number of PC files which contain details of the transfer. Are you able to sanitise these and post them here?
The usual simpke anser is that the field for ‘translate system data to:’ from the ‘details’ prompt in th ePC part of the prompt is not set to BIFF (Basic interchange file format)
experiment with this – and continue to manage the CCSID settings