I spent a month like this, on an always-on system, trying to shut down the upgrade downloader from the task bar whenever I can after failing to stop it from settings, group policy, horsing around in powershell etc. Before that, I had also tried to make the upgrade work by doing it manually, updating drivers, unplugging all the peripherals etc. but it kept getting stuck halfway through. So I couldn't upgrade, and I couldn't not upgrade.
Well last week there was an update to the update so I hoped at least the upgrade would work now and I would be done with this charade. Nope, it crashed again while upgrading, except this time there was no way to roll back and use my system. I am torn between cutting windows out completely and going back to windows 7.