Noob stuck on ESP32-CAM+MB with PIO/vscode

Development Platforms
,
4

I switched to a simple arduino example which flashes a light as provided by PIO home tab and added some println(). The code works (cam flash light if flashing). But when i launch the serial monitor the flashing stops and no trace appears, then if i close (trash icon) the serial monitor the flashing resumes.

#include <Arduino.h>

// Set LED_BUILTIN if it is not defined by Arduino framework
#define LED_BUILTIN 4

void setup()
{
  Serial.begin(115200);
  Serial.setDebugOutput(true);
  Serial.println("Setup starting...");
  Serial.flush();

  pinMode(LED_BUILTIN, OUTPUT);
}

void loop()
{
  digitalWrite(LED_BUILTIN, HIGH);
  delay(5);
  digitalWrite(LED_BUILTIN, LOW);
  
  Serial.println("Waiting 5s...");
  Serial.flush();
  delay(5000);
}