Can't install KB5004237 update

I've been stuck in a loop with this for days and I'm tearing my hair out.

Windows update keeps downloading 2021-07 Cumulative Update version 20H2 KB5004237 and prompts me to restart to install but the same process happens...

Configuring Windows Update
Gets to 7%
Restarting orange screen
Boot screen, followed briefly by a black screen with spinning dots
Restarting orange screen again
Boot screen again
Orange screen saying we couldn't complete update, reverting changes.

I then see on Updates screen, an error code 0x80070003 with the message "Some update files are missing or have problems. We'll try to download the update again later".

I have tried DISM.exe /Online /Cleanup-image /Restorehealth in CMD, and sfc/ scannow and no issues were found, but upon repeating afterwards exactly the same issue.

It wont even install the feature update to windows 10, version 21H1.

I'm currently on build 19042.1052.

Macboatmaster said:

Clean boot it and then try the update please
https://support.microsoft.com/en-us/....%20See%20More

I followed the instructions, restarted, downloaded update again and the same failed process happened as I described in my OP.

Got to 7%, restarted, then rolled back the changes.

Update had same message: Some update files are missing or have problems. We'll try to download the update again later. Error code: (0x80070003)

Macboatmaster said:

You jumped the gun slightly we could have done a repair install and you would have kept everything
Repair Install Windows 10 with an In-place Upgrade

I guess, but I just want to get my pc running again, and so be it if I have to reinstall a bunch of programs and games.

Think the last straw for me was auto repair not being able to fix anything, and the log file apparently being saved in H: drive (OS is on standard C:) and when I looked there was no log file there lol.

I've just got back to desktop and apparently I'm still on 19042.1052 as I was on before, and Windows Update now says there's no updates available? Will this just take time for it to be delivered to me? I want to get this update done and dusted before I commit to loading everything back on.

EDIT: Well the nuke option worked and it downloaded and installed so at least I can get back to reinstating the PC. Wish I knew what it was beyond a likely corrupt registry.

Thanks for your help in the topic Macboatmaster, appreciated.

Macboatmaster said:

Do you use any third party system maintenance software
Many of these include a registry cleaner although not advertised directly as a registry leaner.

I use IOBit Uninstaller 10 which cleans files after uninstalling programs, and driver booster which notifies me of new drivers availability. Everything else is just windows 10 features.