To say Windows 1803 is not the best of Microsoft Updates, is an understatement.
It's not very good at knowing how much disk space it needs to install this update, but > 20GB of free space on drive C: is a good ballpark, < 10GB isn't enough. Good luck with smaller SSDs.
After 13 attempts it still didn't stop attempting to install itself, it's so persistent if it was a person, you'd take out an injunction against them, to stop them stalking you.
Sausage Machine, Conveyer Belt ...the usual shite.