active corners

Perhaps the preferences for your User Account are not being retained due to incorrect permissions. To fix that read Resolve issues caused by changing the permissions of items in your home folder - Apple Support.

I am sorry, but since the problem happens for one user of your machine but not the other, it stands to reason that something specific to that account is involved. Without knowing more specifics, there is little one can do.

If you want, run Etrecheck and post its report. It may shed some light on what you have installed that may cause this.

May be totally unrelated, but from your Etrecheck report I could note a few odd points:

1) You have two very old pieces of software that both were meant to handle NTFS volumes. Neither of them is compatible with Sierra, and have them both can cause all sorts of trouble - including data loss. I suggest that if you need to write to NTFS volumes you stick with one driver and update it to a current version.

Oh wait, I suppose you have three - the paragon software. So uninstall the old stuff.

2) You have Login Items that are currently in the trash. Remove from the login items in System Preferences->Users&Groups.

3) Startup Items are obsolete. They are not doing anything, but for cleanliness you may want to drag the contents of /Library/StartupItems to the trash.

Not that I'm convinced they are the cause, but when you look at the Etrecheck report, it is hard to miss the messages in red. You should deal with them.

1) Login Items: go to System Preferences->Users&Groups, click the padlock, authenticate, select your account, click Login Items, select "Tinytrake", press the "-" button to delete.

2) Startup Items: go to /Library/StartupItems, drag them all to the trash

3) Restart. Your next Etrecheck report should be clean(er)

WAIT!!!!!!!!!!!!

What is this "DrWeb"? Oh! It is an antivirus... DELETE THAT. Uninstall completely.

Antivirus for mac are the source of inumerous problems. They don't protect you from anything, and they cause conflicts with the OS normal operation.

Studio Brand wrote:

I use left bottom active corner for switching between windows of program. In macOS Sierra after switching OS activates other program and I need to press alt+tab for switch in the necessary program. El Capitan had no this mistake.

I am not sure I understand completely.

You have "Application Windows" for the bottom left corner:

Suppose, for example, that you have Mail as the active application and move the cursor to the hot corner.

This should open Mission Control with only the windows Mail. Right?

Are you saying that when you click on one of those windows, another program comes to the front, instead of Mail?

If this is the problem, all I can say is that I can't reproduce it, on either my two macs (both running Sierra).

So I assume this is caused by some software conflict, but is not a universal bug in Sierra.

Try creating a new user account and experiment. Do you see the same problem? (I strongly suspect the answer to be "no").

Next, try restarting in Safe Mode. I am not sure if Mission Control even works in Safe Mode; if it does, test.

In any case, restart normally again and retry. Chances are the cleanup that is done when booting in Safe Mode may have sorted this out.

Let us know.

Studio Brand wrote:

So.. I am in safari. Then I press Mail (standard program), then hot corner. I see mission control with one window of Mail. And I see Safari.

Safe mode not help.

Video: http://brand.dn.ua/1.mov

Thank you for the video. It certainly makes the problem perfectly clear.

When you say safe mode does not help, I suppose you mean that after restarting normally the problem remains.

I need to ask you: does the problem also occur in safe mode itself?

Also, does the problem also occur in another user?

If the answers to the two questions are both "no" (as I suspect they are), please run Etrecheck (from your own account when booted normally) and post its report here.

I have also this problem after upgrading 10.12.1. It's very annoying. Everyday Macs are going to be bore buggy OS ever! I tried everything and no any solution.