This runs, then flails, the restarts.

knight_rider.c

int ledPins[] = {2,3,4,5,6,7,8,9};
  
void setup(){
  for(int i = 0; i < 8; i++){
    pinMode(ledPins[i], OUTPUT);
  }
}
  
void loop(){
  oneAfterAnotherNoLoop();
}

void oneAfterAnotherNoLoop(){
  int delayTime = 50;
  
  for(int i = 0; i < 8; i++){
    digitalWrite(ledPins[i], HIGH);
    delay(delayTime);
  }

  for(int i = 0; i < 8; i++){
    digitalWrite(ledPins[i], LOW);
    delay(delayTime);
  }

  
  for(int i = 7; i >= 0; i--){
    digitalWrite(ledPins[i], HIGH);
    delay(delayTime);
  }

  for(int i = 7; i >= 0; i--){
    digitalWrite(ledPins[i], LOW);
    delay(delayTime);
  }
}