Handle ssh window_adjust message in sftp server

Question

I have sftp server. and when I upload file(SSH_FXP_WRITE) to server(I did it with filezilla client), if the file is bigger than window size, after I send the Window_Adjust_Message, I get 1 or 2 messages of junk data that I can't parse to legal sftp message.

// Ssh library get data on chanel after authontication
OnData(byte[] data)
{
    AdjustWindowMessage((uint) data.Length);
    
    // Send to sftp subsystem to parse and handle request 
    HandleData(data);
}

    AdjustWindowMessage(uint messageLength)
{
    SWindowSize -= messageLength;
    if(SWindowSize <= SMaxSize)
    {
        connection.session.SendMessage(new WindowAdjustMessage
        {
            ResChannel = ClientId;
            BytesToAdd = SInitWindowSize;
        });
        SWindowSize = SInitWindowSize;
    }
}

regular packet size is about 16000 bytes, and 1 or 2 packets that I get after I send the adjust message, is smaller but not always the same size. What is those messages and how shuld I handle it

I didn't figure out if it's buffer of the temp data that has left before I send the adjust message. But I can see, that the first bytes (that from there I have to get the size) is very big.

I saw similar problem but without solution that someone else ask before.

"Message type 93 is not valid in the current context" while uploading via sftp: how to handle/continue?