The malformed response is unrelated to routers I think. The key is here:
Reply: 220-Hello, Welcome to AF SecureTransport!
Reply: 220-
Reply: 220 Secure FTP Server
Command: ---> AUTH TLS
Reply: ready.
Command: ---> QUIT
Reply: 234 SSLv23/TLSv1
There's an erroneous "ready" being returned. The reply "234 SSLv23/TLSv1" is what should be returned in response to "AUTH TLS".
And the wireshark log tells me why:
220 Secure FTP Server\r
ready.\r\n
There's a carriage return after "Server", and edtFTPnet/PRO is reading that as the end of the response. I'll take a look at our code ...