HTTP requests received in wrong time sequence

Question

I am creating an Android app that sends http requests contains IMU data every 20ms using Handler and Runnable.

public void onClickLogData(View view){
        Log.d(TAG,"onClickLogData");
        final OkHttpClient client = new OkHttpClient();

        Handler handler = new Handler();
        Runnable runnable = new Runnable() {
            @Override
            public void run() {
                if (Running) {
                    handler.postDelayed(this, 20);
                    String url = "http://192.168.86.43:5000/server";
                    Log.d(TAG, String.valueOf(time));
                    RequestBody body = new FormBody.Builder()
                            .add("Timestamp", String.valueOf(time))
                            .add("accx", String.valueOf(accx))
                            .add("accy", String.valueOf(accy))
                            .add("accz", String.valueOf(accz))
                            .add("gyrox", String.valueOf(gyrox))
                            .add("gyroy", String.valueOf(gyroy))
                            .add("gyroz", String.valueOf(gyroz))
                            .add("magx", String.valueOf(magx))
                            .add("magy", String.valueOf(magy))
                            .add("magz", String.valueOf(magz))
                            .build();

                    Request request = new Request.Builder()
                            .url(url)
                            .post(body)
                            .build();

                    final Call call = client.newCall(request);
                    call.enqueue(new Callback() {
                        @Override
                        public void onFailure(@NonNull Call call, @NonNull IOException e) {
                            Log.i("onFailure", e.getMessage());
                        }

                        @Override
                        public void onResponse(@NonNull Call call, @NonNull Response response)
                                throws IOException {
                            assert response.body() != null;
                            String result = response.body().string();
                            Log.i("result", result);
                        }
                    });
                } else {
                    handler.removeCallbacks(this);
                }
                }
        };
        handler.postDelayed(runnable, 1000);
    }

And the data are received and stored on my laptop.

with open('imu.csv','w') as csv_file:
        writer = csv.writer(csv_file)
        writer.writerow(['Timestamp','accx','accy','accz','gyrox','gyroy','gyroz','magx','magy','magz'])
        
app = Flask(__name__)
 
@app.route('/server', methods=['GET','POST'])
def server():
    r = request.form
    data = r.to_dict(flat=False)

    t = int(str(data['Timestamp'])[2:-2])
    print(t)
    accx = float(str(data['accx'])[2:-2])
    accy = float(str(data['accy'])[2:-2])
    accz = float(str(data['accz'])[2:-2])
    gyrox = float(str(data['gyrox'])[2:-2])
    gyroy = float(str(data['gyroy'])[2:-2])
    gyroz = float(str(data['gyroz'])[2:-2])
    magx = float(str(data['magx'])[2:-2])
    magy = float(str(data['magy'])[2:-2])
    magz = float(str(data['magz'])[2:-2])
    imu_data = [t,accx,accy,accz,gyrox,gyroy,gyroz,magx,magy,magz]

    with open('imu.csv','a+') as csv_file:
        writer = csv.writer(csv_file)
        writer.writerow(imu_data)
    return("ok")
 
if __name__ == '__main__':
    app.run(host='0.0.0.0')

The requests are sent in chronological order on Android side as Log indicates, however on the receiving side many of the requests are received in wrong time sequence. enter image description here

It seems that this happens more frequently as time goes. What possibly could be the cause of this and where should I be looking at?