The banner comes from the server. We cannot know that is a logic behind it. You need to ask your server/network administrator.

But I guess that your FTP server address is load balanced between multiple FTP servers. And the banner shows you to what actual server you got connected.

I would like to ask one more thing.
In "Welcome(ftp●●)", it randomly displays from "(ftp01)" to "(ftp04)". What is the logic behind this display?

Only the last banner is remembered. So you cannot unfortunately "check ... for all of them".

Thank you for your reply.

As mentioned in my inquiry, I have already checked "Do not show this banner again (N)" in the banner and pressed "Continue" each time.
However, the banner still appears again when I reconnect to the server.

In the attached image, the banner displays "Welcome (ftp04)", but it randomly shows from "(ftp01)" to "(ftp04)".
Even if I check "Do not show this banner again (N)" for all of them, the banner still appears.

Do you know the cause of this issue?
Also, are there any other solutions?

The checkbox disables displaying of that specific banner only. If the contents of the banner changes, it will be displayed.
See the documentation:
https://winscp.net/eng/docs/ui_authenticate#authentication_banner

Hello Mr.Martin,

When launching WinSCP and connecting to a specific server, the "Authentication Banner" shown in the attached image appears. Please review the following details and provide the cause and solution.

▼Details
Even if you check "Do not show this banner again (N)" in the banner and press "Continue" each time, it will be displayed again the next time you connect to the server.
The banner does not appear every time, but about once every two times.
In the attached image, "Welcome (ftp04)" is displayed in the banner, but it is randomly displayed from "(ftp01)" to "(ftp04)".
This issue occurs only with one specific server, although we use multiple servers in our company.

▼Server Information
Transfer Protocol: SFTP
Hostname: 118.21.114.234
Port Number: 22

▼Microsoft Windows Version
Edition: Windows 10 Pro
Version: 22H2

▼WinSCP Version
6.3.4