Windows 11 Update Breaks File History Backups—Check Yours Now

Microsoft has confirmed a frustrating problem with a recent Windows 11 update in its September 2026 Windows security updates: File History can quietly stop creating or updating backups.

That is bad enough on its own, but the symptoms can also be confusing. Windows may tell you to reconnect your backup drive even though it is already connected and working normally. In other cases, the backup date simply stops changing, leaving users with a false sense that their important files are protected.

If you use File History on Windows 10 or Windows 11, now is a good time to check it rather than waiting until you need to restore a missing file.

Microsoft confirms the File History problem

Microsoft added the problem to the known-issues section of its September security update documentation on September 19.

According to the official Microsoft support page for KB5124008, some customers may be unable to create new File History backups or update existing ones after installing the September 2026 Windows security update.

Microsoft says affected PCs can show one or more of these symptoms:

• File History displays a “Reconnect your drive” warning even when the drive is connected.
• The “Last Backup” date and time no longer update.
• Previously backed-up files show “No previous version available.”
• Event Viewer records crashes involving FileHistory.exe and KERNELBASE.dll.

The company has not announced a permanent fix or official workaround yet. Microsoft says it is working on a resolution for a future Windows update.

Which Windows updates are affected?

The problem is listed across multiple September 2026 update pages covering Windows 10 and Windows 11.

Windows version	September update
Windows 11 24H2 and 25H2	KB5124008
Windows 11 26H1	KB5124012
Windows 11 23H2	KB5122880
Windows 10 21H2 and 22H2	KB5122878

Microsoft’s KB5124012 support page lists the same File History warning for Windows 11 26H1. The issue also appears in Microsoft’s documentation for KB5122880 and KB5122878.

That means this is not limited to a single Windows 11 release. Anyone who relies on File History should verify that backups are still running.

How to check File History now

Checking File History only takes a minute:

1. Open the Start menu and search for Control Panel.
2. Select System and Security.
3. Open File History.
4. Check whether Windows recognizes your backup drive or network location.
5. Look closely at the “Last Backup” date and time.

Do not assume everything is fine just because your external drive appears in File Explorer. If the last successful backup predates the September update, File History may no longer be updating your files.

You can also test whether previous versions remain available:

1. Open File Explorer.
2. Right-click a document that should be included in File History.
3. Select Properties.
4. Open the Previous Versions tab.

If Windows unexpectedly says that no previous versions are available, that can be another sign of the confirmed problem.

Advanced users can open Event Viewer and check Windows Logs > Application for recent crashes referencing FileHistory.exe or KERNELBASE.dll.

What to do while waiting for a fix

Microsoft has not published an official workaround, so the safest response is to create a second copy of anything you cannot afford to lose.

You can manually copy important folders to another external drive, NAS, or trusted cloud service. If you already use OneDrive, verify that Desktop, Documents, and Pictures are syncing and that recent files appear on the OneDrive website.

This is also a good time to review our Windows 11 PC setup guide, which explains how to combine local and cloud backups instead of relying on one protection method.

Users preparing to reinstall Windows or move to another PC can also use our WinGet Windows 11 guide to export a list of installed applications. Just remember that a WinGet export is not a backup of personal documents, program settings, or game saves.

Should you uninstall KB5124008?

Some users may be tempted to remove KB5124008 immediately. That can restore affected functionality in certain situations, but it is not the best first step for most people because KB5124008 is a security update.

Uninstalling a security update can reopen vulnerabilities that the patch was designed to fix. Unless File History is business-critical and you understand the security tradeoff, creating a temporary backup with another method is the safer approach.

Microsoft has already released out-of-band updates for some other September problems, including Remote Desktop and portions of a USB audio issue, but its KB5124008 page still lists File History as unresolved. Installing the latest available update is still sensible for security, but users should continue checking the File History status until Microsoft explicitly confirms a repair.

If Windows Update is causing other problems on your PC, our coverage of recent Windows 11 update bugs explains how to pause updates temporarily and evaluate recovery options without rushing into a full reset.

File History users should not wait

Backup failures are easy to ignore because nothing looks wrong until a file disappears or a drive fails. That is what makes this bug more serious than an annoying warning message.

Open File History today, verify the latest backup date, and make a separate copy of your most important files if anything looks suspicious. Microsoft is working on a fix, and we will update this article when a repaired Windows update becomes available.