This question has probably been asked already, as there are reports in the media.
KB4494441 tried to reinstall today 16th May, after being installed on 15th May.
The PC ended in a continuous loop of failing to make changes and undoing changes.
I eventually broke the loop with a forced shutdown, and attempting a system recovery....no clearly defined results.
Somehow the pc is left in a state:-
KB4494441 installed on 15th, KB4494441 failed to install on 16th May.
Don't want to do system restore, as this may start the whole process again.