Hi,
I had upgraded to 1809 on 10/04/18 thru Windows update (clicked on check for updates) and all went well, no problems. I had not previously enabled Known Folder Redirection (KFR). A new build of 1809 has been released to insiders and is being closely monitored.
For the latest information on this issue please see John Cable's blog.
The full address link is:
Hope this helps and Good Luck!
-Richard