const byte ButtonCount = 4;
const byte ButtonPins[ButtonCount] = {2, 3, 4, 5};

const unsigned long DebounceTime = 1000; // just to see the issue better

boolean ButtonWasPressed[ButtonCount];  // Defaults to 'false'
unsigned long ButtonStateChangeTime = 0; // Debounce timer common to all buttons

void setup()
{
  Serial.begin(115200);
  Serial.println("\nWake up!\n"); // wokwi

  for (byte i = 0; i < ButtonCount; i++)
  {
    pinMode (ButtonPins[i], INPUT_PULLUP);  // Button between Pin and Ground
  }
}

void loop()
{
  checkButtons();
}

void checkButtons()
{
  unsigned long currentTime = millis();

  // Update the buttons
  for (byte i = 0; i < ButtonCount; i++)
  {
    boolean buttonIsPressed = digitalRead(ButtonPins[i]) == LOW;  // Active LOW

    // Check for button state change and do debounce
    if (buttonIsPressed != ButtonWasPressed[i] &&
        currentTime - ButtonStateChangeTime > DebounceTime)
    {
      // Button state has changed
      ButtonStateChangeTime = currentTime;
      ButtonWasPressed[i] = buttonIsPressed;
      if (ButtonWasPressed[i])
      {
        // Button i was just pressed
         Serial.print("I see button ");
        Serial.print(i); Serial.print(" go down. ");
        Serial.print(millis());
        Serial.println("");
     }
      else
      {
        // Button i was just released        
      }
    }
  }
}