Nothing yet :(
But additionally I tested for last 2 days Notepad++ (plugin NppFTP) via the same configuration, and there are no any errors, especially like this. So now it is two clients without this problem.

scz11 wrote:

Yes, of course.

And what was his response?

Yes, of course.
We tested situation on FileZilla FTP Client without problems (like this)s, so I put it to WinSCP.

scz11 wrote:

I contacted with server admin and we determined that this error is begin after update proftpd package to version 1.3.5e + r1.3.5-2 due to some security issue.

So did you contact ProFTPD author?

While a session is opened, main window is shown, some file is edited, sometimes it shown error message like "Incoming packet is unreadable after decrypt".
Error screen shot in attachment.
I contacted with server admin and we determined that this error is begin after update proftpd package to version 1.3.5e + r1.3.5-2 due to some security issue.

Using WinSCP 5.15.5 and now 5.15.7 with “Commander” interface on Windows 10.

File transfer protocol = SFTP-3
Cryptographic protocol = SSH-2
SSH implementation = sftp/7.9.1
Encryption algorithm = aes
Compression = No
------------------------------------------------------------
Additional information
The server supports these SFTP extensions:
fsync@openssh.com="1"