Buggy FTP server

We have one buggy FTP-server and no way to fix it.
Periodically its crashes on doenloading file and sent this error:

Another FTP-clients such as FileZilla reconnects quickly and quietly and resuming download,
but WinWSP stops fatal:

Because our traffic going through our Debian 8 firewall, i can substitute text within TCP-sessions on the fly.
I just used nfqsed to change 426 error code to 110 "comment".

iptables -A INPUT -p tcp -s %BUGGY_FTP_IP% --sport 21 -j NFQUEUE --queue-num 0
/root/nfqsed/nfqsed -s /"426 Cannot RETR. EAccessViolation"/"110 Cannot RETR. EAccessViolation" > /dev/null 2>&1 &

According to:
1. devhub.io/repos/rgerganov-nfqsed
2. github.com/rgerganov/nfqsed
3. sysadmin.ru/articles/izmenyaem-soderzhimoe-tcp-paketov-na-letu

This is a very hacky unusual solution, but now WinSCP reconnects and resuming download quickly and quietly.

PLEASE ADD TO WINSCP ABILITY TO IGNORE 426 ERROR AND AUTORESUMING DOWNLOAD.

Please attach a full session log file showing the problem (using the latest version of WinSCP).

log

OK I see. WinSCP does not reconnect, because the FTP connection is actually not closed.

Right, command connection was not losted.

I can repeat this test and logs with my replacement "426" to "110".

log

OK, I'll see if more people ask for this hack.