Windows flickering on macOS (Backingstore issue?)

Sample application attached uses:

• a QMainWindow, with a QLabel and a QQuickWidget side by side
• qml scene consists of a Scene3D with a cube and a default forward renderer
• in main(), forces QSG and Qt3D to use OpenGL backends

On the mac, the app renders but flickers intermittently, often see a white surface across the entire window (including the other widgets, not just the quick widget and qt3d content).

This does not NOT happen if Qt3D is not involved in the QML scene, or if the backends are the default (Metal for RHI, and RHI for Qt3D).

Seems to be an issue how the backing store is rendered, maybe an interaction with how qt3d leaves the GL state?