Hot Corners Yosemite don't work any more

My Macbook Pro (late 2013) running OS X 10.10.4 Yosemite, doesn't respond to Hot Corners any more.

Also, if one application is set to full screen, the Finder keeps stuck / doesn't follow if I change (CMD-Tab) the focus to a different application in a different Desktop (Space). I already tried

• loggin out and in the user account
• restarting the Finder, OS X
• repairing rights while starting up from another partition
• changing hot corners settings, mission control settings
• deleting the ./Library/Preferences/com.apple.dock.plist
• resetting the RMC, PRAM
• I can get back to the main screen / first Desktop with CMD-1 but going back to the full screen application only works with a 4-finger horizontal swipe.
• I noticed Hot Corners work fine with a test accounts, so it must be something with this account.

I've been at this for hours and running out of ideas. Any thoughts?

Update 151203
Recently, I updated to OS X 10.11.1 El Capitan, but this didn't change things.

Update 160214 Did some tests again and noticed the screensaver can be set as a hot corner function, but other functions can not. Also, (with or without fn) Function keys don't work (only in this user account).

In the System Preferences / Keyboard / Shortcuts I used the [Restore Defaults] button. This made the Dashboard function available via Function keys again, but not via Hot corners.

App Expose also only works via the keyboard and gestures Show Desktop and Mission Control don't work at all.

Update 210113
Wow, it's been a while! Since I've updated to Mojave everything works fine. By the I love how this 7+ year old retina MBP 15' still feels as responsive as when I bought it.

I had tried this last year but then it didn't work. I tried it again and now it did work:

Start terminal and execute the following commands:

• defaults write com.apple.dock mcx-expose-disabled -bool FALSE (this enables mission control)
• killall Dock (kill and automatically restart the Dock, this is necessary to get it done)

There is an article about hot corners missing dashboard and mission control.