title: "Scene is modified within a rendering callback of another scene." How to fix this error?
body: <p>I am using ARKit image tracking configuration, once an image is detected, a 3D scene would pop up on the image.</p>
  <p>But when I set two different images to trigger two different scene file, one image always has two different scene files pop up at the same image. I am pretty sure the images are different, the names are different, the scene file are different, the contents of scene are different as well.</p>
  <p>Once the image is detected, below error pops up in the console as well:</p>
  <pre><code>[SceneKit] Error: Scene &lt;SCNScene: 0x284ebcfa0&gt; is modified within a rendering callback of another scene (&lt;SCNScene: 0x28099c820&gt;). This is not allowed and may lead to crash
  </code></pre>
  <p>Any reason and solution for this error?</p>