I have Avast Business Cloudcare a/v on my computer. There's a computer shop very near here. Although that's open to the public, it also deals with providing computer support to businesses in the area and that a/v is through them. So not the free one which many people use though there are similarities. I'm aware that one of the scans provided is a boot time scan not that I've ever needed to use it. I assume that's similar to the one in Windows Defender.
If I discovered that windows update wasn't working and I couldn't sort it out myself I would get that shop to sort it out for me. That did happen once years ago. The latest Windows 10 update last week was successful on my computer.