Looking for someone with experience using guestpref in Ubuntu 16.04 - problem creating a directory

Permissions Problem in Ubuntu 16 using guestpref
Ubuntu 16 has a function (not available in newer versions of Ubuntu) that allows me to set up a user “guestpref” and configure it however I like.
Then when users log in as “guest”, they will be given the exact profile, permissions, desktop etc. of “guestpref”.  When they log out, all traces of that session are erased.

In my guestpref user, I have set up links on the desktop to some audio and video resources mounted on a different server.  
When I'm logged in as guestpref, it works fine - I can access the resources.
But when I'm logged in as guest, I get an error:

Problem:  “Failed to open directory “4-sermons”.  Error opening directory “/tmp/guest-cblvqq/Desktop/4-sermons”:  Permission denied.

Has anyone used the guestpref functionality of Ubuntu 16.04?  Or any guesses about where to turn to address the problem creating a temporary directory beneath /tmp ?

Screenshots attached.


Thanks
guestpref-problem.pdf