program crashes with haarcascade_fullbody.xml - qt

Question

I am working with OpenCV for Qt.
I am working on doing a program which is able to detect several objects. So far I could make a face, eye and nose detector, but when I try to make a full body detection I get either totally wrong detections, no detections at all or the program crashes. For detecting the full body I just use the same code as for the other detections but with the haarcascade_fullbody.xml file. Is it not possible to use the same code? Why does it work for the other features and not for the full body?
I have also tried to implement a car detection using OpenCV's pretrained models from https://github.com/Itseez/opencv_extra/tree/master/testdata/cv/latentsvmdetector/models_VOC2007 but I get parsing errors.
Thanks in advance!
Code from MainWindow:
void MainWindow::on_btnFullBody_clicked()
{
WriteInLog("Full body detection requested");
QString xml = tr("%1/%2").arg(QApplication::applicationDirPath()).arg(FULL_BODY_FILE);
FeatureDetector detector(xml);
std::vector<QRect> rest;
float scaleFactor= 1.1f;
uint neighbours= 2;
bool ret = detector.DetectFeature(&mSelectedImage, rest, scaleFactor, neighbours);
if (!ret)
{
WriteInLog("No full body has been detected");
}
else
{
QVector<QRect> qRect = QVector<QRect>::fromStdVector(rest);
processedImage(qRect);
WriteInLog("Bodys detected: "+QString::number(qRect.size()));
}
}
Code from DetectFeature:
bool FeatureDetector::DetectFeature(QImage* image, std::vector<QRect> &returnList, float scaleFactor, uint neighbours)
{
returnList.clear();
bool ok = false;
qDebug() << "Starting...";
if (!image->isNull()) {
//Changing from QImage to matrix
QImage temp = image->copy();
cv::Mat res(temp.height(),temp.width(),CV_8UC3,(uchar*)temp.bits(),temp.bytesPerLine());
cv::Mat res_gray;
//Changing the image to grey scale an equalizing the result
cvtColor(res, res_gray,CV_BGR2GRAY);
cv::equalizeHist(res_gray,res_gray);
cv::CascadeClassifier detector;
std::vector< cv::Rect > featureVec;
bool retDetector=true; // detector.load("C:/Users/ansurbcn_2/Pictures/cara.jpg");
qDebug()<<mXmlFilePath;
if (!detector.load(mXmlFilePath.toLatin1().constData()))
{
qDebug() << "Error loading detector";
return false;
}
detector.detectMultiScale(res_gray, featureVec);
//detector.detectMultiScale(res_gray, featureVec, scaleFactor, neighbours, 18|9);
if (retDetector) {
qDebug() << "OK Detector";
}
else {
qDebug() << "Failed Detector";
}
for(size_t i=0; i<featureVec.size();i++)
{
cv::Rect oneFeature =featureVec[i];
QRect qrect(oneFeature.x, oneFeature.y, oneFeature.width, oneFeature.height);
returnList.push_back(qrect);
ok = true;
}
}
return ok;
}