C# yer istasyonunda uçuş modu STABILIZE'e atlıyor

using System;
using System.Collections.Generic;
using System.IO;
using System.IO.Ports;
using System.Net.Sockets;

// Kullanim: dotnet run -- COM5 57600   ya da   dotnet run -- tcp 127.0.0.1 5760
Stream akis;
if (args[0] == "tcp")
    akis = new TcpClient(args[1], int.Parse(args[2])).GetStream();
else
{
    var port = new SerialPort(args[0], int.Parse(args[1]));
    port.Open();
    akis = port.BaseStream;
}

const byte HedefSysid = 1;          // aracinin MAV_SYSID degeri
string ekrandakiMod = "?";

var copterModlari = new Dictionary<uint, string> {
    [0] = "STABILIZE", [1] = "ACRO", [2] = "ALT_HOLD", [3] = "AUTO", [4] = "GUIDED",
    [5] = "LOITER", [6] = "RTL", [7] = "CIRCLE", [9] = "LAND", [11] = "DRIFT",
    [13] = "SPORT", [14] = "FLIP", [15] = "AUTOTUNE", [16] = "POSHOLD", [17] = "BRAKE",
    [18] = "THROW", [19] = "AVOID_ADSB", [20] = "GUIDED_NOGPS", [21] = "SMART_RTL",
    [22] = "FLOWHOLD", [23] = "FOLLOW", [24] = "ZIGZAG", [25] = "SYSTEMID",
    [26] = "AUTOROTATE", [27] = "AUTO_RTL", [28] = "TURTLE" };

string ModAdi(uint m) => copterModlari.TryGetValue(m, out var ad) ? ad : $"MOD_{m}";

// Otopilotun HEARTBEAT'i mi? Bilgisayar, gimbal ve yer istasyonu autopilot=8 gonderir.
bool OtopilotMu(byte sysid, byte compid, byte autopilot) =>
    sysid == HedefSysid && compid == 1 && autopilot != 8;

// Otopilot, mesajlari yalnizca kendisine paket gelen porta iletir.
// Bu yuzden yer istasyonu saniyede bir kendi HEARTBEAT'ini gonderir.
byte sira = 0;
using var hbZamanlayici = new System.Threading.Timer(_ =>
{
    var paket = GcsHeartbeat(sira++);
    try { akis.Write(paket, 0, paket.Length); } catch (IOException) { }
}, null, 0, 1000);

var tampon = new List<byte>();
var oku = new byte[512];
while (true)
{
    int n;
    try { n = akis.Read(oku, 0, oku.Length); }
    catch (IOException) { break; }                      // baglanti koptu
    if (n <= 0) break;
    for (int i = 0; i < n; i++) tampon.Add(oku[i]);
    while (CerceveAl(tampon, out byte sys, out byte comp, out uint msgid, out byte[] yuk))
    {
        if (msgid != 0) continue;                       // yalnizca HEARTBEAT
        var p = new byte[9];
        Array.Copy(yuk, p, Math.Min(yuk.Length, 9));    // MAVLink2 sondaki sifirlari kirpar
        uint customMode = BitConverter.ToUInt32(p, 0);
        byte tip = p[4], autopilot = p[5];
        string ham = ModAdi(customMode);
        string not = "";
        if (OtopilotMu(sys, comp, autopilot)) ekrandakiMod = ham;
        else not = " (atlandi)";
        Console.WriteLine($"{sys,3}:{comp,-3} tip={tip,-2} ap={autopilot} mod={customMode,-2} | ham: {ham,-9} | filtreli: {ekrandakiMod}{not}");
    }
}

// Tampondan tek bir MAVLink cercevesi cikarir, CRC tutmazsa cerceveyi atar.
static bool CerceveAl(List<byte> t, out byte sys, out byte comp, out uint msgid, out byte[] yuk)
{
    sys = comp = 0; msgid = 0; yuk = Array.Empty<byte>();
    while (t.Count > 0)
    {
        int bas = t.FindIndex(b => b == 0xFD || b == 0xFE);
        if (bas < 0) { t.Clear(); return false; }
        if (bas > 0) t.RemoveRange(0, bas);
        bool v2 = t[0] == 0xFD;
        int baslik = v2 ? 10 : 6;
        if (t.Count < baslik) return false;
        int len = t[1];
        int imza = v2 && (t[2] & 0x01) != 0 ? 13 : 0;
        int toplam = baslik + len + 2 + imza;
        if (t.Count < toplam) return false;
        msgid = v2 ? (uint)(t[7] | t[8] << 8 | t[9] << 16) : t[5];
        sys = v2 ? t[5] : t[3];
        comp = v2 ? t[6] : t[4];
        ushort crc = 0xFFFF;
        for (int i = 1; i < baslik + len; i++) crc = X25(crc, t[i]);
        // CRC yalnizca HEARTBEAT icin kontrol edilir (crc_extra = 50)
        bool tamam = msgid != 0 || (ushort)(t[baslik + len] | t[baslik + len + 1] << 8) == X25(crc, 50);
        yuk = t.GetRange(baslik, len).ToArray();
        t.RemoveRange(0, tamam ? toplam : 1);
        if (tamam) return true;
    }
    return false;
}

// MAVLink2 HEARTBEAT: sysid 255, compid 190, tip=6 (GCS), autopilot=8 (INVALID)
static byte[] GcsHeartbeat(byte seq)
{
    byte[] p = { 0xFD, 9, 0, 0, seq, 255, 190, 0, 0, 0,
                 0, 0, 0, 0, 6, 8, 0, 0, 3, 0, 0 };
    ushort crc = 0xFFFF;
    for (int i = 1; i < 19; i++) crc = X25(crc, p[i]);
    crc = X25(crc, 50);
    p[19] = (byte)crc; p[20] = (byte)(crc >> 8);
    return p;
}

static ushort X25(ushort crc, byte b)
{
    byte tmp = (byte)(b ^ (crc & 0xFF));
    tmp ^= (byte)(tmp << 4);
    return (ushort)((crc >> 8) ^ (tmp << 8) ^ (tmp << 3) ^ (tmp >> 4));
}

dotnet run -- COM5 57600
  1:1   tip=2  ap=3 mod=4  | ham: GUIDED    | filtreli: GUIDED
  1:191 tip=18 ap=8 mod=0  | ham: STABILIZE | filtreli: GUIDED (atlandi)
  1:1   tip=2  ap=3 mod=4  | ham: GUIDED    | filtreli: GUIDED