Did I just discover "overflow"? All of a sudden, Arduino loop code cannot open the text file (but setup can)

Projects Programming
10

This works, and will write
"debug 1"
"[time], debug 2"

to the text file:

void loop() {
  timeStamp = millis();  // this declaration must be in void loop

Serial.println("debug 1"); //works to this point

  // SD CARD
  myFile = SD.open("zorro.txt", FILE_WRITE);
  if (myFile) {
    myFile.print(timeStamp);
    myFile.print(",");
    //debug 
    Serial.print(timeStamp);
    Serial.print(",");
 /* //BMP Sensor
  //tempC
    char tempCStr[7];
    float tempC = bmp.readTemperature();
    dtostrf(tempC, 1, 2, tempCStr);
/*  //tempF
    char tempFStr[7];
    float tempF = bmp.readTemperature() * (9.0 / 5.0) + 32;
    dtostrf(tempF, 1, 2, tempFStr);
 /* //pressure
    press = bmp.readPressure();
  //alt (m) – 101325 Pa
    char altMStr[12];
    float altM = bmp.readAltitude();
    dtostrf(altM, 1, 2, altMStr);
  //alt (ft) — 101325 Pa
    char altFtStr[12];
    float altFt = bmp.readAltitude() * 3.28084;
    dtostrf(altFt, 1, 2, altFtStr);
  //real alt (m) – 101500 Pa
    char raltMStr[12];
    float raltM = bmp.readAltitude(101990);
    dtostrf(raltM, 1, 2, raltMStr);
  //real alt (ft) — 101300 Pa
    char raltFtStr[12];
    float raltFt = bmp.readAltitude(101990) * 3.28084;
    dtostrf(raltFt, 1, 2, raltFtStr);

    char hypstr[256];
    sprintf(hypstr, "%s,%s,%d,%s,%s,%s,%s", tempCStr, tempFStr, press, altMStr, altFtStr, raltMStr, raltFtStr);

    myFile.println(hypstr); 
    Serial.println(hypstr);
*/
    myFile.println("debug 2"); 
    Serial.println("debug 2");
    
//    char hypstr[256]; //testing min arrays
//    sprintf(hypstr,"%s",tempCStr); //testing min arrays

//    myFile.println(hypstr); 
//    Serial.println(hypstr);
    
        myFile.close();

  } else {
    Serial.println("error opening zorro.txt");
  }
  //END SD card write

  delay(2000);
}

Uncommenting one single array, using sprintf for that one array, and suddenly everything stops working. But it WAS working earlier.

void loop() {
  timeStamp = millis();  // this declaration must be in void loop

Serial.println("debug 1"); //works to this point

  // SD CARD
  myFile = SD.open("zorro.txt", FILE_WRITE);
  if (myFile) {
    myFile.print(timeStamp);
    myFile.print(",");
    //debug 
    Serial.print(timeStamp);
    Serial.print(",");
  //BMP Sensor
  //tempC
    char tempCStr[7];
    float tempC = bmp.readTemperature();
    dtostrf(tempC, 1, 2, tempCStr);
/*  //tempF
    char tempFStr[7];
    float tempF = bmp.readTemperature() * (9.0 / 5.0) + 32;
    dtostrf(tempF, 1, 2, tempFStr);
 /* //pressure
    press = bmp.readPressure();
  //alt (m) – 101325 Pa
    char altMStr[12];
    float altM = bmp.readAltitude();
    dtostrf(altM, 1, 2, altMStr);
  //alt (ft) — 101325 Pa
    char altFtStr[12];
    float altFt = bmp.readAltitude() * 3.28084;
    dtostrf(altFt, 1, 2, altFtStr);
  //real alt (m) – 101500 Pa
    char raltMStr[12];
    float raltM = bmp.readAltitude(101990);
    dtostrf(raltM, 1, 2, raltMStr);
  //real alt (ft) — 101300 Pa
    char raltFtStr[12];
    float raltFt = bmp.readAltitude(101990) * 3.28084;
    dtostrf(raltFt, 1, 2, raltFtStr);

    char hypstr[256];
    sprintf(hypstr, "%s,%s,%d,%s,%s,%s,%s", tempCStr, tempFStr, press, altMStr, altFtStr, raltMStr, raltFtStr);

    myFile.println(hypstr); 
    Serial.println(hypstr);
*/
    
    char hypstr[256]; //testing one array
    sprintf(hypstr,"%s",tempCStr); //testing one array

    myFile.println(hypstr); 
    Serial.println(hypstr);
    
        myFile.close();

  } else {
    Serial.println("error opening zorro.txt");
  }
  //END SD card write

  delay(2000);
}