Why does QFileDialog stay under QWidget?

Question

Qt

Hi all.
Last week I switched from QGLWidget to QOpenGlWidget and noticed a bug that dialog. the window does not appear on the screen. And it remains as I understand it under the main program window.
If I put a breakpoint on the opening line of the dialog. window, everything works as it should.
How can I fix this problem?

initFilePath = QFileDialog::getOpenFileName(this, tr("Open Ini"),
    "C:\\Users\\yuliia\\Documents\\Visual Studio 2013\\Projects\\XPlanQt\\trunk\\res", tr("ini Files (*.ini)"));

Thanks for the help
QT version 5.8