`winget upgrade --all` fails to update winget source, but `winget source update` works

Brief description of your issue

When running winget upgrade --all --include-unknown I was getting:

Failed in attempting to update the source: winget

But this worked:

PS> winget source update
Updating all sources...
Updating source: msstore...
Done
Updating source: winget...
  ██████████████████████████████  100%
Done

Steps to reproduce

Run winget upgrade --all --include-unknown

Expected behavior

The winget source should update itself, before winget upgrade --all --include-unknown checks for available updates.

Actual behavior

winget upgrade --all --include-unknown outputs Failed in attempting to update the source: winget and a number of updates are missing.

Environment

Windows Package Manager v1.4.11071
Copyright (c) Microsoft Corporation. All rights reserved.

Windows: Windows.Desktop v10.0.19045.2965
System Architecture: X64
Package: Microsoft.DesktopAppInstaller v1.19.11071.0

Logs: %LOCALAPPDATA%\Packages\Microsoft.DesktopAppInstaller_8wekyb3d8bbwe\LocalState\DiagOutputDir

User Settings: %LOCALAPPDATA%\Packages\Microsoft.DesktopAppInstaller_8wekyb3d8bbwe\LocalState\settings.json

Links
---------------------------------------------------------------------------
Privacy Statement   https://aka.ms/winget-privacy
License Agreement   https://aka.ms/winget-license
Third Party Notices https://aka.ms/winget-3rdPartyNotice
Homepage            https://aka.ms/winget
Windows Store Terms https://www.microsoft.com/en-us/storedocs/terms-of-sale

Start by reproducing winget upgrade --all --include-unknown and compare its source-refresh behavior with winget source update. Trace the upgrade path that updates the winget source and verify that available updates are detected after the refresh succeeds; the issue provides no file or test location, so project-wide search is required.