title: Failed to execute 'postMessage' on 'Window' GoogleTagManager
body: <p>Recently, I get this <strong>postMessage couldn't be cloned</strong> error. It is happening on most of the latest browsers like Chrome 68, Firefox 61.0, IE11, Edge.</p>
  
  <blockquote>
    <p>Failed to execute 'postMessage' on 'Window': <code>function (a){if(qe.$a.hasOwnProperty(a))return qe.$a[a]}</code> could not be cloned.</p>
  </blockquote>
  
  <p>The stack trace is:</p>
  
  <blockquote>
    <p>Error: Failed to execute 'postMessage' on 'Window': <code>function (a){if(qe.$a.hasOwnProperty(a))return qe.$a[a]}</code> could not be cloned.<br>
    at _reportEvent (eval at  (:1:35637), :94:35)<br>
    at eval (eval at  (:1:35637), :55:5)<br>
    at eval (eval at  (:1:35637), :433:11)</p>
  </blockquote>
  
  <p>Searching through the source of my page in DevTools shows <code>gtm.js</code> as the source of the code fragment:</p>
  
  <p><a href="https://i.stack.imgur.com/HU78B.png" rel="noreferrer"><img src="https://i.stack.imgur.com/HU78B.png" alt="gtm.js shown as source of the function"></a></p>
  
  <p>I have a Google Tag Manager tracking code on my page.  Why is this happening?</p>