As the first tutorial for moving the page file shows, you would not try to set a Page file for C, but instead choose No Paging File for C, then Set.
Then you'd highlight the drive you want the paging file on, and set a System Managed paging file, then Set, then OK.
If this doesn't work it may be a bug in 1809, which was pulled down due to serious problems. You can roll back Version 1809 in Settings>Update & Security>Recovery and then hide it until it matures using the Hide Updates Tool downloaded from here: https://www.howtogeek.com/224471/how-to-prevent...
I hope this helps. Feel free to ask back any questions and let us know how it goes. I will keep working with you until it's resolved.
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