Privs time out
Difficult for me to replicate, however, I was adding a number of printers and setting defaults. I was doing it slowly while doing other things. However, at one point, even though I was actively using the dialog, I had to "re-unlock". In other words, the panel did not seem to appreciate my usage of the dialog as a reset to the counter for privs timeout.
Running: F27, Gnome Version 3.26.2
Edited by langdon