This minor annoyance has been happening often since before Mojave. When I restart or shutdown, I see the spinning rotation busy and even after 10 minutes it is still going. I can power down and boot but I wonder, what can I do to figure out why this is happening? I have scanned the system log and don't see anything obvious to me. If some background app is not quitting, is there some place I can look to see who is at fault?