**Steps to Reproduce**

1. Android SDK, Git already installed. Flutter git was cloned successfully.
2. Running `flutter doctor` in PowerShell

**Logs**

```
C:\flutter>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 ...

```

I'm using NTLM auth behind corporate proxy.