Overview
- Microsoft confirmed on Tuesday that the September 2026 security updates can stop the File History feature from creating or updating backups, affecting Windows versions from 21H2 through 26H1.
- Affected PCs can show wrong messages such as “Reconnect drive,” a non‑updating “Last backup” timestamp, and “No previous version available” for files, with event‑log crashes tied to KERNELBASE.dll and FileHistory.exe.
- Microsoft lists the problem in its Known Issues and says engineers are working on a fix but has not given a date for a patch to restore File History.
- An emergency rollup (KB5129195) has fixed several other September patch problems, yet media and some admins offer conflicting advice about uninstalling the security updates because removing them restores backups but reduces protection.
- The disruption is part of a larger, record‑large September Patch Day that also left persistent audio and GPU driver issues that Microsoft plans to address on the October 13 patch day, creating an ongoing management dilemma for users and IT teams.