GNOME Abrt doesn't consider itself to possess the permission necessary to access a coredump, and also reports that it doesn't exist. Which is it, and why?

What can cause a coredump to “not exist” or be inaccessible due to lack of permission? More confusingly, what would cause both error messages to appear for the same coredump?

Is PolKit dysfunctional, perhaps?

Environment

gnome-abrt-1.4.3-4.fc42.x86_64