Upgrading from Mavericks to Sierra: 1. Clicking any application in dock, 3rd party or Apple, makes the dock animate downward off bottom edge of screen and back upward while both screens flash black for a moment. App is not launched. 2. Clicking documents makes any open Finder windows disappear and reappear and icons the Desktop disappear and reappear. Document not opened and its default app not launched. If one does this several time a dialog window may appear from time to time: "The last time you opened Finder it unexpectedly quit while reopening windows. Do you want to try to reopen its windows again? If you choose not to reopen windows, you may have to open and position the windows yourself." Sometimes the previous open Finder windows do not reappear and I need to click the Finder icon. 3. The only way to use any apps; for instance Safari, is to add it to the Login Items under the Admin account, and restart. If any of these apps are quit they can't be restarted unless you reboot with them added to the Login Items. 4. Tried Disk Utility and reinstall of Sierra via Internet Recovery and did not fix the issue. 5. Booted into safe mode and same symptoms. Erased HD and Completed Fresh Install of Sierra: 1. Worked for several days then the above problem returned after shut down the Mac for one day and restarting it. I usually leave the Mac running and let it fall to sleep, but was going tone gone for the day and thus shut it down. 2. Tried Disk Utility and Reinstall Sierra via Internet Recovery and did not fix the issue. 3. Booted into safe mode and safe problem. Second Everyone Permission In both cases I have noticed that a second "Everyone" with "Custom" privileges has been randomly added to various items by Sierra as thus: Everyone - Custom (my user name) - Read & Write staff - Read only Everyone - Read only Why is Sierra denying access to apps and files? Why is the Finder not working?