QQuickView disappearing on fullscreen with QWebEngineView

Automata

Hello Community,
Please I have set a centralWidget to the mainwindow of my application, which has a grid layout with a QQuickView embedded as both a side bar and a footer, with a central groupbox containing a QWebEngineView which loads a YouTube video. I have shown my QMainWindow in fullscreen. But doing this makes the sidebar and footer QQuickViews disappear, but toggling with the windows key to go out of fullscreen, makes the side and footer banners appear again. Toggling to full screen mode again makes them disappear, and vice versa.

Please note that I am using adobe flash plugins to play the videos from YouTube.

Please any help would be very much appreciated.
Thanks in advance

Automata

What I discovered is that is happening because I have set the spacing on the layout of QMainWindow to 0, as in

setCentralWidget(mainDisplay);
centralWidget()->layout()->setContentsMargins(0,0,0,0);
centralWidget()->layout()->setSpacing(0);

the line:

centralWidget()->layout()->setSpacing(0);

is responsible for this strange behaviour. It works fine on showMaximize but not on showFullScreen