c# socket error 10053 after change buffer size

Question

Im writing a HTTP proxy in c# sockets. Proxy have to make changes in HTML files. Everything works fine until I replace text larger or smaller than originall word was. For example, if I replace "abcde" to "abcde" proxy works perfectly, but if I replace "abcde" to "ab" I got socket exception "An established connection was aborted by the software in your host machine" in socket.send method. I have disabled firewall and windows defender.

Accepting browser socket:

static void Main(string[] args)
    {
        TcpListener tcpl = new TcpListener(IPAddress.Parse("127.0.0.1"), 1024);

        tcpl.Start();

        while (true)
        {
            Socket sock = tcpl.AcceptSocket();
            sock.SetSocketOption(SocketOptionLevel.Socket, SocketOptionName.KeepAlive, true);

            RequestHandler rh = new RequestHandler(sock);

            rh.Handle();
        }
    }

Handle request:

public void Handle()
{
    string header = GetHeader(browserSocket, 1);
    string host = AnalyzeHeader(header);

    if (string.IsNullOrEmpty(header) || string.IsNullOrEmpty(host))
    {
        browserSocket.Close();
        return;
    }
    Socket destServerSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    IPAddress[] addresslist = Dns.GetHostAddresses(host);
    IPEndPoint remoteEP = new IPEndPoint (addresslist[0], 80);
    destServerSocket.Connect(remoteEP);

    SendRequest(destServerSocket, header);

    header = GetHeader(destServerSocket, 0);

    SendRequest(browserSocket, header);       
    int receivedBytes = 1;
    const int BUFSZ = 1024;
    byte[] buffer = new byte[BUFSZ];

    while (receivedBytes > 0)
    {
        if (destServerSocket.Poll(100000, SelectMode.SelectRead))
        {
            receivedBytes = destServerSocket.Receive(buffer, 0, buffer.Length, SocketFlags.None);

            if (header.Contains("Content-Type: text/html"))
            {
                string charset = GetCharset(header);
                charset = string.IsNullOrEmpty(charset) ? "UTF-8" : charset;
                var inputEncoding = Encoding.GetEncoding(charset);
                var text = inputEncoding.GetString(buffer);
                if (text.Contains("abcde"))
                {
                    text = text.Replace("abcde", "ab");
                    buffer = inputEncoding.GetBytes(text);
                    receivedBytes = buffer.Length;
                }

            }

            this.browserSocket.Send(buffer, receivedBytes, SocketFlags.None); //Exception 10053
        }
        else
        {
            receivedBytes = 0;
        }

    }

    this.browserSocket.Shutdown(SocketShutdown.Both);
    this.browserSocket.Close();
}

I have tried to add Content-Length to response header, but error still occur. What do you think the proble is? I've come up to nothing after days of research.