Multiple call of setStyleSheet() cause no effect on children and grand-children widgets inside the QTabWidget/QStackedWidget
I made this simple example to simulate this BUG:

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
    this->setStyleSheet("color:blue;");
    this->setStyleSheet("color:red;");
}

Result can be seen on the screenshot bellow. For the first time, all children and grand-children widgets texts get updated to the blue, but for the second time only direct children widgets are set to the red.