title: JSON syntax error when running page in iFrame
body: <p>I'm developing a website where users can book a table in a restaurant online. Everything's working fine, except one thing: When I put the reservation page in an iFrame on another domain, in a lot of browsers I get an error <code>Unexpected token &lt; in JSON at position 0 at JSON.parse (&lt;anonymous&gt;)</code>. The <code>Network -&gt; Response</code> tab in DevTools tells me, that response data could not be loaded because the request has been redirected.</p>
  <p>This is the page that works well: <a href="https://dev.table4u.de/dimostrazione" rel="nofollow noreferrer">https://dev.table4u.de/dimostrazione</a></p>
  <p>Here I put the page in an iFrame for testing: <a href="https://www.restaurant-zukunft.de/iframe-test" rel="nofollow noreferrer">https://www.restaurant-zukunft.de/iframe-test</a></p>
  <p>This error comes up in a lot of browsers except Firefox, so could this be a problem with formatting the data?</p>