title: flutter doctor - Error: Downloading Dart SDK from Flutter engine
body: <p><strong>Steps to Reproduce</strong></p>
  
  <ol>
  <li>Android SDK, Git already installed. Flutter git was cloned successfully.</li>
  <li>Running <code>flutter doctor</code> in PowerShell</li>
  </ol>
  
  <p><strong>Logs</strong></p>
  
  <pre><code>C:\flutter&gt;flutter doctor
  Checking Dart SDK version...
  Downloading Dart SDK from Flutter engine ead227f...
  Start-BitsTransfer : flutter doctor - 69/5000 The resource loader cache doesn't have a loaded MUI entry . (HRESULT: 0x80073B01 Exception)
  En C:\flutter\flutter\bin\internal\update_dart_sdk.ps1: 47 Character: 1
  
  Start-BitsTransfer -Source $dartSdkUrl -Destination $dartSdkZip
    + CategoryInfo          : NotSpecified: (:) [Start-BitsTransfer], COMException
    + FullyQualifiedErrorId : System.Runtime.InteropServices.COMException,Microsoft.BackgroundIntelligentTransfer.Mana
   gement.NewBitsTransferCommand
  
  Error: Unable to update Dart SDK. Retrying...
  
  Waiting 2 seconds, press CTRL+C to exit ...
  </code></pre>
  
  <p>I'm using NTLM auth behind corporate proxy. </p>