Full Breakdown
Windows File History Breaks After September 2026 Update; Optional Preview Update Provides Temporary Fix
By Drooid · · How we work
Core Event: File History Backup Failure After September 8 Patch
The mandatory September 8, 2026 Patch Tuesday update (KB5124008) introduced a bug that stops File History from creating or updating backups on Windows 10 and Windows 11. Affected systems show a “Reconnect your drive” alert even when the backup drive works, and the “Last backup” timestamp often fails to refresh, leaving users with “No previous version available” messages. Event Viewer may log entries referencing FileHistory.exe and KERNELBASE.dll.
Background & Context
File History, accessed via Control Panel -> System and Security -> File History, backs up user libraries (Documents, Pictures, Videos, Music, Desktop) to an external or network drive. Microsoft lists the feature in support documentation but encourages migration to OneDrive or Windows Backup.
Timeline
- September 8, 2026 – Security update KB5124008 rolls out, triggering File History failures.
- September 14, 2026 – Emergency update KB5129195 released; it does not address File History.
- September 22, 2026 – Optional preview update (KB5124010) patches File History for most recent Windows 11 builds.
- October 13, 2026 (scheduled) – Upcoming Patch Tuesday update is expected to include a permanent fix.
Data & Statistics
- Affected Windows 11 builds: 26H1, 25S2, 24H2 (patched by the preview); 23H2 remains unsupported.
- Windows 10 devices enrolled in the Extended Security Updates (ESU) program receive the September patch and experience the same issue.
- Microsoft’s support page notes the bug occurs across all current Windows versions from 21H2 through 26H1.
Official Statements & Responses
Microsoft says the “Reconnect your drive” alert is a false positive caused by the bug, not hardware failure. The optional preview update released on September 22 “should start working properly again” for supported builds, and a comprehensive fix is slated for the October 13 Patch Tuesday rollout.
On-the-Ground Reports
Users report persistent “Reconnect your drive” warnings despite functional drives, missing “Last backup” timestamps, and inability to retrieve prior file versions. Some also encounter a separate issue where clicking Execute now in the File History control panel fails to synchronize the backup timestamp.
Conflicting Reports & Gaps
- Scope of the preview fix: ZDNet reports the optional preview does not apply to Windows 11 23H2 or Windows 10, while PCWorld suggests the fix will be incorporated into the October Patch Tuesday update for all versions.
- Long-term resolution: Microsoft has confirmed a future update will address the bug, but coverage for Windows 10 ESU devices remains unclear.
What’s Next
The October 13, 2026 Patch Tuesday is expected to deliver a permanent resolution for all affected editions. In the interim, users should install the optional preview update (KB5124010) via Settings -> Windows Update -> Optional updates, or rely on OneDrive or Windows Backup for critical file protection.