Alt + Tab has two actions for me: Close selected application and Switch between applications - it says here in my Unity Keyboard Shortcuts HUD (holding the Super key)

After having upgraded my machine from Ubuntu 14.04.x to 16.04.01 I ran into very unexpected behaviour:

Whenever I press Alt+Tab (I run Unity as my desktop env.) two things happen: I switch to the next application AND closes the currently active application.

I searched for a solution (or a bug report or something helpful) for some hours now and finally I came upon the Keyboard Shortcuts HUD (holding the Super key) which gave me (e.g.) the following list:

__Switching__

* Alt + Tab: Switches between applications
* Ctrl + Alt + Tab: Switches between application from all workspaces
* Alt + 1: Switches windows of current applications
* Cursor Left or Right: Moves the focus
* Cursor Up or Down: Enter / Exit from spread mode or Select windows
* Alt + Tab: Closes the selected application / window

Link to a screenshot: https://twitter.com/ulrikkold/status/771440559424700417

You will notice there are two registered actions for the Alt+Tab shortcut combination. This is useless. Especially with application that do not ask for confirmation before closing. They just shut down and I have to restart the application to pick up where I left.

I still have not been able to find a somewhere to configure / reset the two actions for that same key combination.

I also have not been able to find a bug report on this issue - so I choose to think this is a configuration issue and that I will be able to have Alt+Tab do one thing and one thing only: Switch between applications as it always did in any windowed environment I worked in.

I have NOT tried to switch to a different DE and I have NOT tried a clean install of Ubuntu 16.04.

Please, help me finding a solution. Working with Alt + 1 in combination with the Cursor keys (or simply using the mouse) is simply not as powerful as switching directly with Alt+Tab. It's a pain to avoid that worked-in shortcut. It's working against muscle memory.