This is a bit of a weird one, not sure why it's happening.
We've got a very structured nesting of our courses and categories - partly for security but mostly to make it easier for administrators to navigate them all. For courses that are two categories deep (hidden or not), everything works as you would expect - you can edit, assign roles, enter the course, backup, restore, etc. For ANY course that's more than two categories deep (hidden or not), you can only move the courses up or down, or into another category. You cannot edit, assign roles, enter the course, backup, restore, etc. If you try to enter these courses, you are presented with whatever the enrollment options are (not enrollable, enrollable, key required) - even though you're an administrator.
Originally, I had $CFG->max_category_depth=2 in config.php, but even increasing this or removing it does not change this.
I've attached some screenshots that might make it easier to follow. Looks like the bug tracker reorders them, view in this order: cat_list1, course_list_cadd, course_list, acct, course_enter.