Sometimes Windows update files become corrupted.
Glad it worked out.
You have Win 10 Pro, so you can defer feature updates for up to 365 days. What I do is to choose when I want to upgrade, and do it manually. That way I
- make sure I have an up to date disk image before I upgrade, in case things go badly
- perform the upgrade at my convenience
- avoid any complexities with Windows update and feature upgrade
- have the iso ready for further attempts if necessary without downloading again
- wait to upgrade until at least the first major update AFTER the build release is released.
I recommend you
- create a new base disk image of Windows (e.g. Macrium Reflect (free) + external storage) - disk imaging is strongly and repeatedly recommended here
- enable System Restore (if considering using it - it's probably disabled now)
- defer feature updates (Settings or Group policy as you prefer).
You may also like to set updates to 'Notify' - another useful feature for Pro users.