Fix ERROR_FLT_INTERNAL_ERROR (0x801F000A) on Windows

Quick answer

Restart the Filter Manager service (FltMgr) from an elevated Command Prompt with net stop FltMgr then net start FltMgr. If that fails, run sfc /scannow followed by DISM /Online /Cleanup-Image /RestoreHealth.

What's going on?

The 0x801F000A error code maps to ERROR_FLT_INTERNAL_ERROR, which means a filter driver inside the Windows Filter Manager framework threw an internal exception. I've seen this across Windows 10 21H2, 22H2, and Windows 11 23H2 machines. It usually pops up when you're running backup software (like Acronis, Veeam, or Macrium Reflect) or security suites that use kernel-mode filters — think antivirus tools from McAfee, Bitdefender, or even Microsoft Defender during a system scan. The error can also appear after a Windows update that patches the FltMgr.sys file but doesn't restart the service cleanly.

The frustrating part? The error shows up in Event Viewer under System logs with source “FltMgr” and ID 0x801F000A, and it'll cause unexpected program crashes, blue screens (BugCheck 0x801F000A), or just fail to load a third-party driver. But the root cause is almost always a corrupt or hung filter driver instance. Here's how to kill it.

Step-by-step fix

Stop the Filter Manager service
Open Command Prompt as Administrator. Right-click Start, select “Windows Terminal (Admin)” or “Command Prompt (Admin)”.
Type: net stop FltMgr and press Enter.
What you'll see: “The Filter Manager service is stopping.” Then “The Filter Manager service was stopped successfully.” If you get a message saying “The service cannot be stopped,” jump to the alternative fixes below.
Start the service fresh
Same window, type: net start FltMgr
What you'll see: “The Filter Manager service is starting.” Then “The Filter Manager service was started successfully.”
Check for corrupt system files
After restarting the service, run: sfc /scannow
That scans all protected system files. Let it finish — can take 15 minutes on a spinning drive, less on an SSD.
What you'll see: “Windows Resource Protection found corrupt files and successfully repaired them.” If it says “found corrupt files but was unable to fix some,” go to step 4.
Use DISM to fix the image
If SFC found files it couldn't repair, run: DISM /Online /Cleanup-Image /RestoreHealth
This pulls fresh copies from Windows Update. If you're offline, you'll need a valid install.wim from a USB drive — but that's rare.
What you'll see: Progress bar, then “The restore operation completed successfully.”
Reboot
Restart the computer. Not optional. The filter driver stack resets during boot.
Test the fix
Try whatever triggered the error originally. For example, if it was a backup job, run a manual backup now. If it was a security scan, kick off a quick scan. No error? You're good.

Alternative fixes if the service won't stop

If net stop FltMgr hangs or throws an access denied error, the filter driver is pinned by an active process. Do this:

Kill the offending process first
Open Task Manager (Ctrl+Shift+Esc), go to Details tab, sort by CPU or Memory, look for anything from your backup or antivirus app. Right-click it, End task. Then retry step 1.
Boot into Safe Mode
Hold Shift while clicking Restart from the Start menu. Troubleshoot > Advanced options > Startup Settings > Restart > press 4 for Safe Mode. In Safe Mode, the filter stack is minimal. Run net stop FltMgr again — it'll work now. Then disable the problematic third-party filter driver: open regedit, go to HKLM\SYSTEM\CurrentControlSet\Services\, find the driver key (common names: avc3, snapfilter, bkupfilter), set Start to 4 (disabled). Reboot normally.
Uninstall the recent update
If the error started after a Windows Update, go to Settings > Windows Update > Update history > Uninstall updates. Remove the latest Quality Update (KBxxxxxxxx). Reboot.

Prevention tip

Keep your third-party filter drivers updated. I've seen old versions of Macrium Reflect's ReflectDriver.sys and Symantec Endpoint Protection's SymEFASI.sys cause this error repeatedly. Check the vendor's site for a filter driver update after every Windows feature update. Also, if you run multiple security products, uninstall one — they fight over the filter manager priority list and trigger this error faster than you can say “kernel panic.”