Camera animation frozen when using QQuickRenderControl

I'm using QQuickRenderControl to render QML offscreen. I'm using private Rhi APIs as recommended in QTBUG-88876. I am animating the camera position. This works fine until I introduce a 2D element inside a Node as described in https://doc.qt.io/qt-6/qtquick3d-2d.html

Once a Node with a 2D Rectangle is introduced, the camera animation stops working.

I have code to reproduce this at https://github.com/rectalogic/rendercontrol3d

https://github.com/rectalogic/rendercontrol3d/blob/master/main.cpp is nearly verbatim lifted from tst_RenderControl::renderAndReadBackWithRhi() in qtdeclarative/tests/auto/quick/qquickrendercontrol/tst_qquickrendercontrol.cpp - except it dumps the rendered image to a PNG every 25 frames.

After building the sample, run build/rc3dtest <qml-file> to dump the PNG snapshots.

https://github.com/rectalogic/rendercontrol3d/blob/master/rect3d-camera-2d.qml animates the camera Z position. The View3D contains a Node with a 2D Rectangle.

Run with build/rc3dtest rect3d-camera-2d.qml

In the image snapshots you can see the camera does not move at all. The camera Z position is shown in a toplevel Text field and also in a Text inside a Node. The Z position shown in the Node is at each snapshot is 500-496-496-496-496,  it does not change after the second dump. The same Z position in the top level Text correctly changes from 500-400-300-200-104. See attached screenshots.

If you simply remove the Node/Rectangle inside the View3D, then everything works - the camera animates. Run build/rc3dtest rect3d-camera-no2d.qml to see this.

Finally build/rc3dtest rect3d-cube-2d.qml animates the cube itself, not the camera. Even though it also contains a Node/Rectangle, it works fine.

So there seems to be some strange interaction when using QQuickRenderControl and animating the camera while the View3D scene contains a 2D Rectangle inside a Node. The other variations described above all seem to work fine.