Microsoft Fixes Windows File History Backup Failure After September 2026 Update

Microsoft has fixed a known issue that caused the built-in File History backup feature to stop working on some Windows systems after users installed the September 2026 security update.

File History, introduced for Windows 8, replaced Windows Backup and automatically backs up a user’s account profile, including documents, music, photos, videos, and the desktop.

The feature saves copies to an external hard drive, such as a USB flash drive, or to network storage (NAS). Users can then recover files that were accidentally deleted or corrupted by restoring older versions saved hours, days, or weeks earlier.

Windows File History showed false drive errors

According to a Microsoft service notice, the September 2026 security update could cause File History to stop creating or updating backups. The issue could also trigger an application crash referencing FileHistory.exe and KERNELBASE.dll in Event Viewer.

On affected systems, users saw a “Please reconnect the drive” warning even when a compatible backup drive was connected and working properly.

Other symptoms included:

• Previously backed-up files showing “No previous versions”.
• The “Last Backup” timestamp failing to update.
• File History failing when backing up or restoring files to an external drive or network location.

Microsoft said the problem affected systems running Windows 10 21H2 or later, Windows 10 Enterprise LTSC 2016 and 2019, and Windows 11 23H2 or later.

Microsoft fixes File History in September 2026 preview updates

Microsoft announced that the issue has been fixed for Windows 11 users in the September 2026 optional cumulative updates. The fixes are included in KB5124006 for Windows 11 26H1 and KB5124010 for Windows 11 24H2 and 25H2.

“This update addresses an issue that could cause File History to fail when backing up or restoring files to an external drive or network location,” Microsoft said.

“We recommend that you install the latest updates for your device as this update contains important improvements and resolutions to issues.”

File History fix coming with October Patch Tuesday

Windows users who do not want to install the optional preview update will receive the fix in the next month’s Patch Tuesday update, scheduled for October 13, 2026.

Microsoft also released an out-of-band update a week earlier to address Remote Desktop Services failures, Hyper-V issues involving host folder shares in Linux virtual machines, and USB audio problems caused by the September Patch Tuesday security update.

A few days later, Microsoft shared a temporary workaround for a separate bug that prevented some Windows 11 users from logging in with valid domain credentials after installing the same update.

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