Microsoft Defender on-demand file scanner sometimes doesn't scan


barreleye

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This has been going on for a couple of weeks, so it's a new problem. I've always disabled real-time AV and used the on-demand file scanner, and scanning a downloaded file by selecting "Scan with Microsoft Defender..." from the context menu is something I do many times per week. (Never had a virus or malware, and I've been using Windows since 3.0.) Lately, perhaps half of these actions result in this window being immediately displayed, indicating the scan didn't take place:

1668208527552.png

When this happens, I have to go back and right-click the file and just do it all over again to get the expected result, e.g. (for anyone unfamiliar, there's a transient progress bar and file counter that go away when it's finished, so they're not depicted)

1668208585193.png

To be clear, this is scanning a single file, an archive of some sort. This is not a quick scan. I got to these screens by right-clicking the file and running "Scan with Microsoft Defender..." from its context menu.

Can anyone say if this is a known problem? It started very recently for me, probably no more than a couple weeks ago.
 
Windows Build/Version
Windows 11 22H2 (OS Build 22621.819)

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  • OS
    Windows 11

oldschool

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Windows 11 Pro 22H2
I'm on the same OS build and no problems here. Have you tried to reset Defender app?
 

My Computer

System One

  • OS
    Windows 11 Pro 22H2
    Computer type
    Laptop
    Manufacturer/Model
    Lenovo IdeaPad L340
    CPU
    Intel Core i3-8145U
    Memory
    8GB
    Internet Speed
    45MB
    Browser
    Firefox | Edge
    Antivirus
    Microsoft Defender | Block all unknown executables | Various ASR rules enabled

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