Seeing how the ftp-deploy-sync-state.json file exists on your account and in the right directory, it means that the GitHub Action is able to upload the files to FTP.
So it seems that uploading files works, however this specific CSV file is causing problems.
Did you read this article already that @Frank419 shared?
Especially the file size limit is something to be aware of, which should be 10 MB for a CSV file. How big is the file you’re trying to upload?
And have you tried uploading this file with the file manager or a desktop FTP client also?