Guest can't shut down
I have an iMac and am running the latest version of OS (10.13.1). The computer is running well with one small hitch. When the Guest User account is accessed and either chooses "Shut Down" or "Log Off" is chosen, the iMac doesn't shut down properly - I get the outline of an arrow across a black screen. In order to shut down, I must depress the the power button. I have done some trouble shooting, but to no avail. Suggestions welcome!
MacBook Pro (Retina, 15-inch, Late 2013), Version 10.11.5