On the 6th July 2021 my Win 10 Pro automatically installed the KB5004945 update. After this update my PC would no longer complete the boot.
I initially thought it was my HDD so I reverted to an earlier cloned backup disk which booted normally. I was able to link the 'failing' drive to my system and found that all the files were okay and I could copy all the changed files to the now reverted version.
Then when I shut down Windows again downloaded the quality and feature updated automatically and installed them before powering off.
Little did I realise that the problem was the Microsoft KB5004945 update that was corrupting my OS and preventing the boot from completing.
After some searched on Google (using my phone) I found a process for going into repair mode and uninstalling the latest updates. As a result of uninstalling KB5004945 the boot completed perfectly and I was back to my old Win10 Pro desktop. Whew!!
So now I set the update service process to only update when I approve it manually.
I'm running Windows 10 Pro on a Dell Optiplex 9010 with 1TB HDD.