Very Small bug in IMU_USB_v5_0.ino with step down

I made this kind of small box for my IMU with a step down and an HC-05. So I can place them wherever I want on my tractors.

However, I encountered a problem. in this configuration the arduino seems to launch too quickly and does not give the BNO time to start. therefore he cannot find it. I therefore suggest simply adding:

  void setup()
    delay(5000); //delay for start BNO
    Serial.begin(38400);  // Start serial port

this does not happen when powered by USB. I suppose that the step down takes a (tiny) time to stabilize at 5 V, and that the arduino starts before unlike the BNO.