What FTP client(s) work for uploading to pond5?

I have tried filezilla and cyberduck, but the upload never finish because it re-uploads the same files over and over again. I have reached out to support but they said will not troubleshoot 3rd party software. I notice the problem does not happen unless each file takes a few minute to upload - this leads me to think a timeout setting on the server side/firewall. However support simply refuses to troubleshoot and blame it on the ftp client that I am using. Yet filezilla is recommended on their seller faq. So I am stuck with footages that I can not upload. The web interface often result in upload errors when upload batch size is large (100+). What ftp client works reliably on pond5?

I had same problem with Filezilla.

Switched to WinSCP - no more issues.
Suggest also FTP'ing in groups of files - for example groups of 10.

I think Andftp is the best solution to upload files on pond5