Hot corners enabled via the Unity tweak tool in Ubuntu 16.04 do not work properly after rebooting. I've seen that this bug has been present since 14.04 and it has been reported on Launchpad, but it was just "confirmed". Should I report the bug again?
If the bug has already been reported on Launchpad, don't file a duplicate. Instead, you should click on "Does this bug affect you?" and then click on "Yes, it affects me". If you want to provide more details in the form of screenshots or logs, then make a post on the bug report with these details so that the devs have more useful information to work with.