title: Firefox DevTools: Console & Network panel broken with "ReferenceError: IntersectionObserver is not defined"
body: <p>In a normal firefox from &quot;release&quot; software channel, I have this error in the network panel:</p>
  <p><a href="https://i.stack.imgur.com/N77Is.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/N77Is.png" alt="error in network panel" /></a></p>
  <p>This error is only shown in network panel. The console panel is just completely blank .</p>
  <p>The other panels (inspector, debugger, style editor...) are all working fine.</p>
  <p>Installed addons:</p>
  <ul>
  <li>cookie quick manager</li>
  <li>web developer (<a href="https://addons.mozilla.org/en-US/firefox/addon/web-developer/" rel="nofollow noreferrer">see addons.mozilla.org</a>)</li>
  </ul>
  <p>I have another profile running which works fine! (=&gt; so I guess it's not the firefox installation)</p>
  <p>My guess would be that one of the addons causes problems, but error stays even in &quot;Troubleshoot mode&quot; (with all addons disabled)</p>
  <p>Web searches for this specific error message all point to concrete problems with react, nothing that I could make sense of for my problem.</p>
  <p>Anybody seen this? What can I do to investigate/test further?</p>