Windows 11 File History Bug Leaves September Backups Silent and Stale
Microsoft has confirmed that its September 2026 security updates can stop File History from creating or updating backups on Windows 10 and Windows 11, in a patch cycle that also disrupted Remote Desktop sessions and audio. The Windows 11 File History bug traces to KB5124008, the September 8 security update for versions 24H2 and 25H2 (builds 26100.9445 and 26200.9445), and it does not announce itself. The backup panel opens normally, the external drive stays connected, and the last-backup timestamp simply stops moving.
Affected machines show failure symptoms rather than a clean crash. File History can display a "Reconnect your drive" prompt while a compatible backup disk is attached and working, and Event Viewer records crash events for FileHistory.exe and KERNELBASE.dll. Files archived in earlier months can return a "No previous version available" message when someone tries to restore them.
The scope reaches well past Windows 11. Microsoft lists Windows 10 21H2 and later, Windows 10 Enterprise LTSC 2016 and 2019, and Windows 11 23H2 and later as affected, with the fault distributed across six packages: KB5122876, KB5122878, KB5122880, KB5123099, KB5124008 and KB5124012.
The Scope of the Windows 11 File History Bug
Microsoft's servicing documentation records File History as a known issue for the September rollout, logged publicly on September 19 and expanded into a wider alert on September 21. That is roughly two weeks after the original patch reached Windows Update.
| Update | Shipped | Builds | File History status |
|---|---|---|---|
| KB5124008 (security) | September 8, 2026 | 26100.9445 / 26200.9445 | Introduced the regression |
| KB5129195 (out-of-band) | September 14, 2026 | 24H2 / 25H2 | Did not address File History |
| KB5124010 (optional preview) | September 22, 2026 | 26100.9550 / 26200.9550 | Partial repair, opt-in install |
| KB5124006 (optional preview) | September 22, 2026 | 28000.3086 (26H1) | Preview channel |
Two entries in that timeline shape how users should respond. The September 14 out-of-band release, KB5129195, resolved the Remote Desktop and audio faults that dominated early complaints, yet it left the backup regression untouched. Corrective code for the Windows 11 File History bug only arrived on September 22 with KB5124010, and that build is an optional preview rather than a mandatory security update.
The difference between the two update types sits at the centre of the problem. Security updates install automatically by default, which is how the fault reached machines in the first place, while preview updates install only when a user asks for them or enables early access. The remedy therefore waits behind a gate that most affected users have no reason to have opened.
Why a Silent Backup Failure Costs More Than a Crash
A crashing application gets noticed within minutes. A backup that quietly stops writing new versions can go undetected for weeks, and the damage is measured in the distance between the last good copy and the day someone needs it.
That gap is where the real risk sits. File History covers the full user profile by default, copying Desktop, Documents, Pictures, Music and Videos to a USB drive or network share, a behavior Microsoft has shipped since Windows 8. Someone checking the File History panel sees a connected drive and an enabled feature, while the spurious reconnect prompt pushes them toward hardware troubleshooting instead of the update that caused the problem.
Verification carries its own cost. Anyone who has trusted File History through September should confirm the last successful copy before relying on any restore, then run a fresh backup once the fix is installed. Work created during the outage window was never captured, and no patch recovers files that were never written.
The exposure scales with how much a machine changes. A personal laptop that gains a handful of documents each week loses little; a workstation producing design files, photographs or code every day loses a month of distinct versions that the backup set should have held. File History keeps multiple generations of each file, so a stalled backup does not merely delay protection, it erases the restore points that were never created.
The Fix Is Optional, and Only Partial
KB5124010 arrives through the preview channel, so it installs only when a user opts in to receiving updates early or installs it manually. Microsoft's release notes pair the File History repair with a fix for the built-in camera failing in the Camera app and other camera-using applications.
Windows 11 version 24H2 sits at the end of its preview run: the September 2026 non-security preview is the last monthly preview Microsoft will publish for that branch. Owners of 24H2 who want the File History correction through the normal update stream must wait for the October security release.
The documented workaround is a rollback. Microsoft's support guidance points to uninstalling KB5124008 through Settings, then pausing Windows Update so the package is not reinstalled before a permanent fix ships. Removing a security update reopens whatever vulnerabilities it closed, which makes this a short-term trade rather than a repair.
Timing compounds that trade-off. Rolling back KB5124008 means running without September's security fixes until the next mandatory release in October. Users who choose the rollback should treat it as a deliberate decision with a scheduled end date, not a permanent configuration.
What to Do Now
Open File History and read the last-backup timestamp before assuming anything is protected. A date that predates the September security update means the machine is affected. On 24H2 and 25H2, installing KB5124010 and triggering a manual backup is the quickest route back to a functioning state.
Where the preview build is not available, a manual copy of critical folders to a second drive or a network location keeps data moving in the interim. The regression is specific to File History's own engine, so a plain file copy is not affected by it.
Machines on Windows 10 21H2 or later, and on Enterprise LTSC 2016 or 2019, have no equivalent preview package listed, so their owners should watch Microsoft's servicing notes for a servicing-channel repair. Other faults reported in the same cycle, including Remote Desktop failures and AMD GPU driver timeouts, were addressed by the mid-month out-of-band release.
Why this matters
The Windows 11 File History bug failed in the manner most likely to cause harm: silently, while displaying the status signals users are trained to trust. An installed update is not proof of a working backup, and until Microsoft moves the correction into the regular security channel, checking the timestamp is the only reliable way to know whether a Windows machine is genuinely protected.
Sources
Windows 11 September 2026 update cycle — Microsoft support servicing page
File History stopped working after a recent update ...
Photo by Pham Nhat on Unsplash
Related Articles
- Windows 11 Emergency Update KB5129195 Fixes Broken Remote Desktop, Hyper-V and Audio
- Windows 11 September 2026 Update Puts the Taskbar Back Where You Want It
- Record September 2026 Patch Tuesday: 974 Fixes, Two Live Zero-Days, and an Overloaded Triage Pipeline
✔Human Verified
Researched and cross-referenced against primary sources by the Bytevyte editorial team. This article was generated with the assistance of artificial intelligence and reviewed by the Bytevyte editorial team.