title: Attempt to perform arithmetic on field 'x' when reloading a scene
body: <p>I'm getting an error message: <code>Attempt to perform arithmetic on field 'x'</code> while trying to reload a scene that I previously loaded.</p>
  
  <p>I found that the error occurs due to the following line:</p>
  
  <pre><code>bg1.x = bg1.x - scrollSpeed
  </code></pre>
  
  <p>What can I do to fix this issue? </p>
  
  <p>Thanks!</p>