Program: 4196
Project: 4196
Buggy source:
/** 
 * Registers functions that map TimeFields to a human readable description.
 */
private void registerFunctions(){
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof Always) {
      if (timeFields.seconds instanceof Always) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
      }
      if (timeFields.seconds instanceof On) {
        if (isDefault((On)timeFields.seconds)) {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
        }
 else {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.seconds).getTime().getValue());
        }
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (isDefault((On)timeFields.seconds)) {
        if (isDefault((On)timeFields.minutes)) {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
        }
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.minutes).getTime().getValue());
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.minutes).getTime().getValue(),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof On && timeFields.seconds instanceof Always) {
      return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue());
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (isDefault((On)timeFields.seconds)) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue());
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue(),((On)seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof Always && timeFields.seconds instanceof Always) {
      return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue());
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof Between) {
      if (timeFields.seconds instanceof On) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getFrom().getValue(),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getTo().getValue());
      }
      if (timeFields.seconds instanceof Always) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getFrom().getValue(),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getTo().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof Every && timeFields.seconds instanceof On) {
      Every minute=(Every)timeFields.minutes;
      String desc;
      if (minute.getPeriod().getValue() == 1 && isDefault((On)timeFields.seconds)) {
        desc=String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
      }
 else {
        desc=String.format("String_Node_Str",bundle.getString("String_Node_Str"),minute.getPeriod().getValue(),bundle.getString("String_Node_Str"));
      }
      if (minute.getExpression() instanceof Between) {
        desc=String.format("String_Node_Str",desc,describe((minute.getExpression())));
      }
      return desc;
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Every && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (((On)timeFields.minutes).getTime().getValue() == 0 && ((On)timeFields.seconds).getTime().getValue() == 0) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
      }
      String result=String.format("String_Node_Str",bundle.getString("String_Node_Str"),((Every)hours).getPeriod().getValue(),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)minutes).getTime().getValue());
      if (isDefault((On)timeFields.seconds)) {
        return result;
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
}

Fixed version (ground truth):
/** 
 * Registers functions that map TimeFields to a human readable description.
 */
private void registerFunctions(){
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof Always) {
      if (timeFields.seconds instanceof Always) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
      }
      if (timeFields.seconds instanceof On) {
        if (isDefault((On)timeFields.seconds)) {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
        }
 else {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.seconds).getTime().getValue());
        }
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (isDefault((On)timeFields.seconds)) {
        if (isDefault((On)timeFields.minutes)) {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
        }
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.minutes).getTime().getValue());
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.minutes).getTime().getValue(),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof On && timeFields.seconds instanceof Always) {
      return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue());
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (isDefault((On)timeFields.seconds)) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue());
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue(),((On)minutes).getTime().getValue(),((On)seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof Always && timeFields.seconds instanceof Always) {
      return String.format("String_Node_Str",bundle.getString("String_Node_Str"),((On)hours).getTime().getValue());
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof On && timeFields.minutes instanceof Between) {
      if (timeFields.seconds instanceof On) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getFrom().getValue(),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getTo().getValue());
      }
      if (timeFields.seconds instanceof Always) {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getFrom().getValue(),bundle.getString("String_Node_Str"),((On)timeFields.hours).getTime().getValue(),((Between)timeFields.minutes).getTo().getValue());
      }
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Always && timeFields.minutes instanceof Every && timeFields.seconds instanceof On) {
      Every minute=(Every)timeFields.minutes;
      String desc;
      if (minute.getPeriod().getValue() == 1 && isDefault((On)timeFields.seconds)) {
        desc=String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
      }
 else {
        desc=String.format("String_Node_Str",bundle.getString("String_Node_Str"),minute.getPeriod().getValue(),bundle.getString("String_Node_Str"));
      }
      if (minute.getExpression() instanceof Between) {
        desc=String.format("String_Node_Str",desc,describe((minute.getExpression())));
      }
      return desc;
    }
    return "String_Node_Str";
  }
);
  descriptions.add(timeFields -> {
    if (timeFields.hours instanceof Every && timeFields.minutes instanceof On && timeFields.seconds instanceof On) {
      if (((On)timeFields.minutes).getTime().getValue() == 0 && ((On)timeFields.seconds).getTime().getValue() == 0) {
        Integer period=((Every)timeFields.hours).getPeriod().getValue();
        if (period == null || period == 1) {
          return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"));
        }
      }
      String result=String.format("String_Node_Str",bundle.getString("String_Node_Str"),((Every)hours).getPeriod().getValue(),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)minutes).getTime().getValue());
      if (isDefault((On)timeFields.seconds)) {
        return result;
      }
 else {
        return String.format("String_Node_Str",bundle.getString("String_Node_Str"),bundle.getString("String_Node_Str"),((On)seconds).getTime().getValue());
      }
    }
    return "String_Node_Str";
  }
);
}