title: XCode 12.4 : An Internal Error Occurred Editing functionality may be limited
body: <p>Since upgrading to XCode12.4 on two different MacBooks both running macOS 10.15.6 I have issues opening Storyboard / Xib files.</p>
  <p>Just to be clear this doesn't occur for a specific project - this happens for <em>any</em> project I open and for <em>any</em> storyboard / xib file within that project.</p>
  <p>There is a long delay before the file opens and when it does I see.</p>
  <ol>
  <li><p>The UI Components in blue outline rather than the details.</p>
  </li>
  <li><p>The Error Message: An Internal Error Occurred Editing functionality may be limited</p>
  </li>
  </ol>
  <p>From my log.txt</p>
  <pre><code>XCODE VERSION INFO:
  
  Version = 12.4 (12D4e)
  Plugin Version = 17701
  Beta Version = 1
  OS Version = 10.15.6 (19G2021)
  
  
  ASSERTION:
  
  Failed to update scene '01J-lp-oVM' with IBUIViewAutolayoutGuide (x1), UIView (x1), and UIViewController (x1).
  
  Exception name: IBPlatformToolFailureException
  Exception reason: The tool closed the connection
  
  Application Specific Information:
  ** Terminating app due to uncaught exception 'NSInternalInconsistencyException', reason: 'Failed to create remote render context'
  
  terminating with uncaught exception of type NSException
  abort() called
  CoreSimulator 732.18.6 - Device: iPhone Xʀ (9B855293-1F8D-4794-BF54-5193C46BB094) - Runtime: iOS 14.4 (18D46) - DeviceType: iPhone Xʀ
  </code></pre>
  <p>I've cleaned derived data / restarted my machine etc - all to no avail.</p>
  <p>All I can do at this stage is reinstall XCode 12.4 unless anyone can make any suggestions?</p>