The following is based on the Quick3d/View3d example (the one with the 4 green teapots).

The rendering result is scaled (zoomed) when I dynamically change the far clipping plane of an OrthographicCamera used within a View3D.

The relevant portion of main.qml is this:

// Stationary orthographic camera viewing from the top
Node {
  OrthographicCamera {
    id: cameraOrthographicTop
    y: 600
    eulerRotation.x: -90
    clipFar: 800
    onClipFarChanged: print("clipFar= " + clipFar)
 }
  Timer {
      interval: 100; repeat: false
      //running: false; // v1, rendering ok
      //running: true; // v2, rendering scaled
      onTriggered: cameraOrthographicTop.clipFar = 801
  }
}

        
The v1 line creates the view shown in "v1 - ok.png". The lower left teapot is nicely rendered.

The v2 line only updates the clipFar value once (from the timer), causing the rendered result to be scaled ("v2 - scaled.png"). This is not expected behavior, as adjusting the far clipping plane of an OrthographicCamera should not result in scaling.

I have not checked for other circumstances that show similar behavior (clipNear, perspective camera, etc.).