Our application packs serialized XML datasets, and sends over FTP to the main server, running FileZilla 0.9.44, released yesterday. We've also tried it on 0.9.27.
Among about 70 clients, just one gets an error message while uploading a 5 MB binary file to the Filezilla FTP server, "An existing connection was forcibly closed by the remote host", from FileZilla server, and exactly after 2 minutes, every time. Each client uses it's own user credentials, all in same user group, and user settings are the same with others on Filezilla server.
I've checked router settings to see if there's a blocking setting. OS is Windows XP, many other clients run on too.
Edit: We've tried FileZilla client for sending the same file and same exception thrown. But Filezilla is able to resume after reconnect.