This worked for me; thank you for the suggestion.

BUT... I'm back to why I left the Insider builds in the first place. After a reboot, I'm stuck in a bluescreen-loop with "CRITICAL_PROCESS_DIED."...

I'm having the exact same problem. I switched from Release Preview to Fast. I noticed that if I switch back to Release Preview the error goes away.

Event Viewer has three WindowsUpdateFailure3...