My production machine again proved to be the difficult one.

It was the first to download them and ask for a reboot but, of the seventeen updates,  it managed only nine. A second run at the other eight saw them all install as Microsoft intended. Now, it keeps offering the Defender rollup time and again.

The Windows 7 machines all updated without a fuss and as far as I am aware are showing no adverse effects.

There’s little else that I can say. I keep all machines as clean as possible, make as few system changes as is possible and as a consequence have very few problems indeed with updates. There is no secret way to ensure reliability.