QQuickWindow fails to fire visibleChanged signal when in a QTabWidget

I have a QTabWidget which contains a QQuickWidget. The widget renders based on a model that does some quite heavy lifting, therefore I have it set up to only perform the calculations when the QQuickWidget is actually visible.

Previously (Qt 5.12.0), I could do this by connecting to the QQuickWidget's quickWindow() via the &QQuickWindow::visibleChanged signal - this would trigger whenever the tab changed to either show or hide the QQuickWidget, and I could then turn updates on or off. This no longer appears to work.

Example attached - with Qt 5.12.0 switching between the tabs will pop-up a message box displaying the visible state of the QQuickWidget. With Qt 5.12.7 there is no indication that the signal connection fails, but the lambda never fires.