I don't believe Windows Defender would cause this problem.
I suggest you do an InPlace Upgrade. This procedure reinstalls Windows.
But don't worry. You have the option to keep files, settings, and apps.
- Download the Media Creation Tool and run it;
Access the link below and click on "Download tool now".
https://www.microsoft.com/software-download/win...
- Accept the terms of use;
- Select "Upgrade this PC now" and click "Next";
- At the "Ready to install" screen, select "Choose what to keep" and select what you want to keep.
- Click "Install" and wait for the procedure to finish. Your computer may restart several times.
The update will likely be installed during InPlace Upgrade. Therefore, it should no longer appear on Windows Update.