Windows 10: How to resolve an Antimalware problem that began with the most recent Windows 10 update

Ever since the March 9, Windows Update, the Antimalware Service Executable has been running continuously 15+ hours of full scan without terminating. I'm running Windows 10 Home version 20H2. Task Manager doesn't allow me to kill the process, which very seriously slows down my PC and hogs resources. I've already tried running a Microsoft Defender Offline scan, which terminated normally after 15 minutes and restarted with no scan. That helps for a while, but the scan starts up again and continues to run interminably. Nothing like this every happened before this latest, most unwelcome update. Any ideas?

:)

 

Windows 10 Tweaks

Pressing “Windows+Pause Break” (it’s up there next to scroll lock) opens the “System” Window.

Windows 10: In the new version of Windows, Explorer has a section called Quick Access. This includes your frequent folders and recent files. Explorer defaults to opening this page when you open a new window. If you’d rather open the usual This PC, with links to your drives and library folders, follow these steps:

• Open a new Explorer window.
• Click View in the ribbon.
• Click Options.
• Under General, next to “Open File Explorer to:” choose “This PC.”
• Click OK

credit to Lifehacker.

 

New install Windows 10 (issue solved)

It's good that you're not experiencing any issues. Unfortunately many folks are, a quick Google search will show the same info im offering the OP.

Heres a couple examples:

Here

Here

It's basically what I mentioned above, small issues here and there ,but nothing to end your day.. for the most part.

I know it's anecdotal, but for my experience 95% of the time it's perfectly fine. The issues I've run into wouldn't be enough for me to roll back , but they would be enough (had I not installed it yet) ,to avoid it for another couple weeks which is why I'm suggesting it to the OP

Windows 10 Fall Creators Update problems and complaints

• Installation problems with the Fall Creators Update
• Microsoft Edge problems with the Fall Creators Update
• Drivers problems with the Fall Creators Update
• Experience problems with the Fall Creators Update

keep in mind, as of recently, the FCU is installed on 5% of devices roughly.....

 

Windows 10 fails to update


Thanks,

The Users list compared to the Profile list you posted earlier tell me there is not an issue with Users (a known issue where there is a profile in the list, but not actual User folder).

The error code suggests corruption in the CBS manifest:
Try these steps one at time until the issue is resolved or you run out of steps.

Is Windows activated?
No? Activate Windows 10

Launch Command Prompt (Admin)
enter the following line
reg query HKLM\Software\Policies\Microsoft\Windows\WindowsUpdate /s
If DisableWindowsUpdateAccess REG_DWORD 0x1

launch regedit
navigate to HKEY_LOCAL_MACHINE\Software\Policies\Microsoft\Windows\WindowsUpdate
change the value of DisableWindowsUpdateAccess to 0
exit regedit
exit Command Prompt

Launch Windows Update

Try the next suggestion if the issue is not resolved.

Restore health to the component store
DISM - Repair Windows 10 Image
Step 6. To Use DISM /RestoreHealth /Source:wim Command
- OR -
Step 7. To Use DISM /RestoreHealth /Source:esd Command
Check System Files
SFC Command - Run in Windows 10
Read the front material, then
follow >> OPTION THREE <<
To Run SFC /SCANNOW Command in Windows 10

If there are integrity issues reported on screen,
Follow the instructions in >> OPTION FIVE <<
To View Only the "SFC" Scan Results from the CBS.LOG

If there are no integrity errors, Launch Windows Update

Try the next suggestion if the issue is not resolved.

Paste the following line into the address bar of File Explorer
Control Panel\All Control Panel Items\TroubleshootingLaunch System and Security > Fix problems with Windows Update
Press Advanced
Select Run as administrator
Press Next

Launch Windows Update

Try the next suggestion if the issue is not resolved.

Automatically reset Windows Update components
Download and run MS Windows Update diagnostic cab (direct download)

Launch Windows Update

Try the next suggestion if the issue is not resolved.

Manually reset Windows Updates via batch file

Windows Update - Reset in Windows 10

Launch Windows Update