Manual reset required after upload in one on 4 upload attempts

[michalwoz]

I'm using Arduino Mega 2560 board with simplest possible connection to W5500 Ethernet modules. Just 7 wires, nothing else. I tested 2 clones with CH340 and one original board. Tested three different power sources. Most upload attempts are successful. Sometimes, after one on 3-10 uploads program don't start. I need to reset board manually. After manual reset NEWly uploaded, correct program wakes up.

I use only OTA, MQTT, buttons ant PWM, but I think that it is not dependent on the sketch.

void setup() {
  delay(1500); //testing with delay, tried with and without that
  Ethernet.begin(mac, ip);
  delay(1500); //That comes from pubsubclient, tried with and without that

  ArduinoOTA.begin(Ethernet.localIP(), "controller2", "password", InternalStorage);

  Timer3.initialize(1000);
}

Is there any known issues with that?