The machine I have been using Mojave on has had one or more folders in the \Users folders get corrupted and rendered inaccessible. The short version of this fix was to make a copy of the most previous version of the corrupt folder, shut down, boot with the Mojave install DVD, go to recovery, get to the command prompt, then run chkdsk C: /f, then pray a bit, then see if things got fixed and if you need to recover.
What a load of warthog feces.
The pain-in-the-ass is not being able to run the chkdsk from the Mojave GUI or when the computer is restarted (via prompt when you try to run the GUI chkdsk). You can tell it over and over and over again but it never seems to run chkdsk.
This corruption has occurred after installing software and after installing updates. Apparently, others have run into this problem.