Memory Leak during construction, only while in debug mode, QtWebEngine

I'm on Windows 10, using MSVC2015.
I'm trying to use the QtWebEngineView. It works well in release mode (QtCreator), but crashes regularly in debug mode. It consumes serveral GB of memory before doing so. Sometimes it does, sometimes it doesn't.
It's always when creating a new page

zcMMPage::zcMMPage(zcMMViewerWebEngine *viewer, QObject *parent)
    : QWebEnginePage(parent), _viewer(viewer)
{
    qDebug() << "zcMMPage in constructor";
}

The constructor never reaches the debug statement.

I reprogrammed the whole solution using QML and QtWebEngine. The QQuickWidget shows the same behaviour:

zcMMViewerQml::zcMMViewerQml(QWidget *parent)
    : QQuickWidget(parent)
{
    qDebug() << __FUNCTION__ << "zcMMViewer";

    qDebug() << "QQuickWidget";
    QQuickWidget *_quick = this;
    _quick->setResizeMode(QQuickWidget::SizeRootObjectToView);
    qDebug() << "QML Source";
    _quick->setSource(QUrl("qrc:/mm/zcmmview.qml"));
    qDebug() << "Connect QML Signals";

(..)

It just never reaches the " qDebug() << _FUNCTION_ << "zcMMViewer";
" statement.

It looks like both problems point in the same direction.
Both consume GBs of memory before giving up.

It only appears in debug mode