During FTP upload the transfer fails with "Could not write to transfer socket: EPIPE"

Each FTP connection consist of two TCP connections: a mandatory control connection, and, during active transfers, the data connection. During a transfer the control connection of the FTP stays completely idle. If you are behind a misconfigured firewall or router that closes the control connection, the file transfer fails.

You can either try a different FTP upload program or contact your IT department for assistance.