The Slow Rollout of Windows 10 21H1

Why you need this article

On May 18, Microsoft started rolling out its latest Windows 10 feature update, known as Windows 10 21H1, to mainstream users. For the past several months, 21H1 has been in testing with Windows Insiders.

The next version of Windows 10 called "21H1", or the May 2021 Update, is available to users running Windows 10 2004 or later as an optional update in Windows Update.

The Windows 10 21H1 feature update is a very small release and does not bring too many new features. However, it does come with performance and security enhancements that will improve the operating system's overall experience, making it worth installing.

Microsoft is first making Windows 10 21H1 available as an optional update to "seekers," or those who manually perform a check for new updates, running Windows 10 2004 or later. Microsoft will later make it available to further Windows 10 users after being tested with a smaller group at first.

Installing the Update

Windows 10 21H1 is available to "seekers." This means Windows users who are running "select devices" with Windows 10 2004 or later can proactively seek it out by going to Start Menu > Settings > Update & Security and click on the Check for updates button. Windows 10 will perform a quick check and then list the optional 'Feature update to Windows 10, version 21H1, which you can install by clicking on the Download & install now link.

As Microsoft has been doing lately with Windows 10 feature updates, it will be throttling the delivery of the 21H1 update, delivering it first to devices where it is likely to have fewer issues. As has been the case recently, Microsoft will likely issue "safeguard holds," designed to prevent the feature update from installing on devices where there are known issues and incompatibilities.

Microsoft noted that Insider testers in the Beta and Release Preview channels are already on the "newer" 21H1 bits as of earlier this month.

If you are having troubles installing, please reference this article LINK

What’s new

While a new version of Windows 10 is now available, Windows 10 21H1 is not a very exciting release with many new features.

Instead, it is being released more as a service pack that fixes bugs and includes performance improvements for existing features. As part of the new features, version 21H1 (May 2021 Update) won’t significantly change the way you use Windows 10. Instead, it will focus on some key areas, including quality, remote access, and security.

Use an external camera as default for Windows Hello

For those using a Windows-Hello-compatible external camera with a PC that already has a built-in camera, Windows automatically uses that external camera as the default for Windows Hello.

Access documents faster and more securely

Microsoft brought improvements to Windows Defender Application Guard so that your documents open faster, while still checking for possible security concerns. Windows Defender Application Guard helps prevent untrusted Word, PowerPoint, and Excel files from accessing your trusted resources.

Most of the new features in Windows 10 21H1 are instead targeted to business users and the remote workforce. These new features are:

  • New Windows Hello multi-camera feature – detailed above
  • News and interests widget for Windows 10 21H1 taskbar
  • Windows Mixed Reality – new feature to set the sleep timer for headsets
  • Windows Defender Application Guard (WDAG) improvements – detailed above
  • Windows Management Instrumentation (WMI) Group Policy Service (GPSVC) improvements
  • New Microsoft Edge (Chromium) support for kiosk mode on Windows 10 May 2021 Update
  • WinHTTP Web Proxy Auto-Discovery Service improvements
  • Updates the Open Mobile Alliance (OMA) Device Management (DM) sync protocol
  • Windows 10 startup times for apps with roaming settings improvements on version 21H1
  • Windows Server Storage Migration Service new feature to migrate from NetApp FAS arrays to Windows Servers and clusters


  • New support for using the new Chromium-based Microsoft Edge as the assigned access single kiosk app.
  • Improves startup times for applications that have roaming settings when User Experience Virtualization (UE-V) is turned on.
  • Updates the Open Mobile Alliance (OMA) Device Management (DM) sync protocol by adding a check-in reason for requests from the client to the server. The check-in reason will allow the mobile device management (MDM) service to make better decisions about sync sessions. With this change, the OMA-DM service must negotiate a protocol version of 4.0 with the Windows OMA-DM client.
  • Turns off token binding by default in Windows Internet (WinINet).
  • New dfslogkey in HKEY_LOCAL_MACHINE/SOFTWARE/MICROSOFT/dfslog. The RootShareAcquireSuccessEvent field has the following possible values, including a default value of 1 to enable the log, and a value other than 1 disables the log.
  • Improves the ability of the WinHTTP Web Proxy Auto-Discovery Service to ignore invalid Web Proxy Auto-Discovery Protocol (WPAD) URLs that the Dynamic Host Configuration Protocol (DHCP) server returns.
  • Enhances data loss prevention and insider risk management solution functionalities in Microsoft 365 endpoints.


Microsoft has started slowly rolling out the May update, "21H1", to select seekers. There are a number of 'quality of life' improvements and bug fixes for business users as well as a few changes for general use. As Microsoft gradually deploys this update, more and more users will receive the update, hopefully Microsoft will avoid any major hangups and address any critical failures earlier rather than later. As always, if you have any questions please don't hesitate to reach out to Puget Systems Support team.

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Bug Fixes

Some of the more technical/business related bug fixes are listed below. Most of them will not apply to a standard user but instead apply to very specific tasks and business practices.

  • Fixed an issue that prevents a site from transitioning out of Microsoft Edge IE Mode when expected.
  • Addressed a problem that fails to remove mandatory profiles completely when you sign out when using the “Delete cached copies of roaming profiles” Group Policy.
  • Fixed an issue that causes blank tiles to appear on the Start menu with names such as “ms-resource:AppName” or “ms-resource:appDisplayName.”
  • Addressed a problem with the Microsoft Japanese Input Method Editor (IME) that prevents an app’s custom candidate window from displaying correctly.
  • Fixed an issue that occurs when you install inventory applications.
  • Addressed a problem that includes kernel-mode rules for .NET applications in Windows Defender Application Control policies. As a result, the generated policies are significantly larger than necessary.
  • Fixed an issue that causes devices to fail Device Health Attestation.
  • Addressed a problem that turns off S Mode when you enable System Guard Secure Launch on a system running Windows 10 in S Mode.
  • Fixed an issue that causes “lsass.exe” memory usage to grow until the system becomes unusable.
  • Addressed a problem with a race condition between Task Scheduler and the Workstation Service.
  • Fixed an issue that causes Azure Active Directory authentication to fail after signing in on Windows Virtual Desktop machines.
  • Addressed a problem that causes AAD Work Accounts to unexpectedly disappear from certain apps such as Microsoft Teams or Microsoft Office.
  • Fixed an issue with a partial Service Connection Point (SCP) configuration that causes dsregcmd.exe to stop working.
  • Addressed a problem that accidentally triggers hybrid AAD joining when the Group Policy “Register domain-joined computers as devices” is set to DISABLED.
  • Fixed an issue that might generate a stop error when Docker containers run with process isolation.
  • Addressed a problem that causes automatic enrollment and certificate retrieval to fail with the error, “The parameter is incorrect.”
  • Fixed an issue that might cause Microsoft Defender Application Guard virtual machines to stop responding when Microsoft Defender Application Guard for Office opens a document.
  • Addressed a problem that prevents some media players from playing content on hybrid devices that are running with dGPU on iGPU displays.
  • Fixed an issue with race conditions that cause high CPU usage.
  • Addressed a problem with a deadlock in the New Technology File System (NTFS).
  • Fixed an issue that causes DWM.exe to stop working in some cases.
  • Addressed a problem that might prevent an application screen from working when using a Remote Desktop ActiveX control that is embedded in an HTML page.
  • Fixes an issue causing 0xC2 (BAD_POOL_CALLER) bug check when using IOCTL_SCSI_PASS_THROUGH_DIRECT.