The Windows 11 September 2026 security update KB5124008 has broken File History backups for businesses across Kent and the South East, leaving SMEs unable to create or update critical file backups despite functioning backup drives being properly connected.
After installing the September 2026 Windows security update KB5124008, customers using File History might be unable to create or update backups, with affected devices incorrectly displaying a “Reconnect your drive” message even when a compatible backup drive is connected and functioning properly.
This issue affects any Kent SME relying on Windows’ built-in File History feature for data protection, and it’s the second major failure introduced by KB5124008 following the Active Directory domain trust problems we reported earlier this month. For office managers and business owners who’ve configured File History as their primary backup solution, this defect creates a dangerous gap in business continuity planning.
What File History Backup Failures Look Like on Windows 11
File History, available through Control Panel > System and Security > File History, is used to back up files to an external drive or network location.
Kent SMEs affected by the KB5124008 issue report several symptoms:
- False “Reconnect your drive” error messages despite backup drives being properly connected
- The “Last Backup” timestamp not updating, and previously backed up files showing “No previous version available”
- Event Viewer recording application crash events referencing FileHistory.exe and KERNELBASE.dll
- Inability to create new backups or restore files from existing backup sets
This represents a critical data protection failure. Businesses believing their files are being backed up may discover—only when attempting recovery—that no backups have been created since early September 2026.
Why This Backup Failure Matters for Kent SMEs
File History provides version control and recovery for business documents, spreadsheets, presentations and other critical files stored in user libraries, desktop folders and OneDrive. Many Kent SMEs implement File History as their primary protection against accidental deletion, file corruption and ransomware encryption.
With
nearly half (49%) of UK SMBs experiencing a cyber incident in the past year, with 13% experiencing more than one incident
, the ability to restore clean file versions becomes essential during recovery operations. A three-week gap in backup coverage—from 8 September when KB5124008 deployed until 22 September when the fix arrives—creates significant exposure.
Kent businesses relying exclusively on File History now face the risk of permanent data loss if file corruption, accidental deletion or ransomware encryption occurs during this window. The issue is particularly concerning because the false “Reconnect your drive” message actively misleads users into believing the problem lies with their hardware rather than Microsoft’s update.
Additional Risks from September 2026 Patch Tuesday
The File History failure arrives during a record-breaking security month.
Microsoft released fixes for 974 vulnerabilities across Microsoft products in September 2026, representing a 70% increase over the previous single-month record of 569 Microsoft-only CVEs set in July 2026.
This unprecedented patch volume increases the likelihood of conflicts, compatibility issues and unintended consequences like the File History defect.
Two actively exploited zero-day vulnerabilities—CVE-2026-85880 in Windows Advanced Local Procedure Call (ALPC) and CVE-2026-81963 in the Windows Update Stack—were included in this release
, forcing Kent SMEs into a difficult position: delay patching and remain vulnerable to active exploits, or patch immediately and lose backup protection.
This tension between security updates and operational stability has become a defining challenge for UK SMEs in 2026, particularly given Microsoft’s recommendation to deploy Windows updates within three days.
Microsoft’s Fix Timeline and What Kent SMEs Must Do Now
Microsoft confirms this issue is resolved in Windows updates released on and after 22 September 2026.
For Kent businesses affected by File History failures, the immediate priorities are:
1. Verify Your Backup Status Immediately
- Open Control Panel > System and Security > File History
- Check the “Last Backup” timestamp—if it shows a date before 8 September 2026, your backups have stopped
- Check Event Viewer (Application log) for FileHistory.exe crash events
- Document which business-critical files have not been backed up during the outage
2. Deploy the 22 September 2026 Cumulative Update
Install the latest Windows update released on or after 22 September 2026. This will be delivered through Windows Update as a cumulative update that supersedes KB5124008 whilst preserving the security fixes from the September Patch Tuesday release. Restart devices after installation to ensure the fix takes effect.
3. Verify Backup Restoration After Patching
After applying the fix, confirm File History resumes normal operation:
- Force a manual backup through File History settings
- Verify the “Last Backup” timestamp updates correctly
- Test file restoration by recovering a known file version
- Monitor Event Viewer to confirm FileHistory.exe crashes have stopped
4. Consider Interim Backup Alternatives
For the gap period between 8 September and your deployment of the 22 September fix, consider temporary backup measures:
- Manual copies of critical files to external drives or network shares
- Cloud backup to OneDrive, SharePoint or third-party services
- Image-based backups of entire systems using Windows Backup or third-party tools
Long-Term Backup Strategy Recommendations for Kent Businesses
The KB5124008 File History failure highlights the risks of relying on a single backup method, particularly one integrated into the operating system that receives monthly security updates. Kent SMEs should implement defence-in-depth backup strategies that include:
- Multiple backup technologies: Combine File History with cloud backup and periodic image backups to ensure redundancy
- Automated verification: Regular restore testing to confirm backups are functioning and recoverable
- Monitoring and alerting: Automated checks that notify IT staff when backups fail or become stale
- Offsite and offline copies: Protection against ransomware that targets network-attached and cloud-connected backup repositories
This incident also reinforces the importance of staged patch deployment. Rather than deploying updates to all devices immediately, test new patches on a small group of non-critical systems for 48-72 hours before wider rollout. This approach would have identified the File History failure before it affected business-critical systems.
Related Issues Affecting Kent SMEs This Month
The File History failure is one of several KB5124008 defects affecting Kent businesses in September 2026. Earlier this month we reported on Active Directory domain trust failures that prevented users from logging into domain-joined devices, and Remote Desktop Services failures on Windows Server 2025 following related September 2026 updates.
These quality issues arrive at a particularly challenging time.
The latest UK Government Cyber Security Breaches Survey shows 50% of UK businesses experienced a cyber incident in 2024, rising to 74% for medium businesses
, creating pressure to patch quickly whilst simultaneously dealing with patch-induced failures that disrupt operations.
Get Expert Help with Windows Update Management
Managing the tension between rapid security patching and operational stability requires expertise, testing infrastructure and monitoring capabilities that many Kent SMEs lack in-house. Meridian Micro Limited provides managed IT support that includes staged patch deployment, backup verification and rapid response when updates cause operational issues.
If your Kent business has been affected by the KB5124008 File History failure, or if you need help implementing robust backup strategies that protect against both cyber threats and patch-induced failures, call our Saltwood team on 01303 883111 for immediate assistance. We serve SMEs across Hythe, Folkestone, Canterbury, Ashford and the wider South East with expert IT support designed for businesses that cannot afford downtime or data loss.