When using QT_SCALE_FACTOR qcombobox items cannot be clicked

AleixQ

Scaling app using this environment variable set to anything but 1 (e.g 0.5 or 2) leads to qcombobox unusable as items cannot be selected or have an offset. The same happens when adding a qdialog with Qt:Popup window flag.
I am using Arch linux with Qt 5.15.2.
Here is the code to test:

#include <QApplication>
#include <QTreeView>
#include <QStandardItem>
#include <QVariant>
#include <QComboBox>
#include <QGroupBox>
#include <QHBoxLayout>
#include <QVBoxLayout>
#include <QMainWindow>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    QMainWindow* MainWindow = new QMainWindow();
    QGroupBox* MapPane = new QGroupBox(MainWindow);
    MapPane->setGeometry(QRect(0, 0, 694, 510));
    QVBoxLayout* verticalLayout = new QVBoxLayout(MapPane);
    QHBoxLayout *mapFilterCtrl = new QHBoxLayout();
    QComboBox *combo1 = new QComboBox(MapPane);
    QComboBox *combo2 = new QComboBox(MapPane);
    QComboBox *combo3 = new QComboBox(MapPane);

    QStringList fonts = { "AAAA", "BBBB", "CCCC", "DDDD" };
    combo1->addItems(fonts);
    combo2->addItems(fonts);
    combo3->addItems(fonts);

    mapFilterCtrl->addWidget(combo1);
    mapFilterCtrl->addWidget(combo2);
    mapFilterCtrl->addWidget(combo3);
    verticalLayout->addLayout(mapFilterCtrl);

    MainWindow->setCentralWidget(MapPane);


    MainWindow->show();

    return a.exec();
}