On my main account, Alt-Tab works just fine, however, I just created a second user, and the application switcher is completely messed up, there seem to be two interfaces displayed on top of each other, as can be seen in the image below:
I already tried rebooting multiple times, but the problem remains.
I'm using Ubuntu 16.04.
Thanks to David Foerster, I resolved it:
I installed the Compiz Config Settings Manager:
And then under
Window management
, I disabled theApplication Switcher
plugin.Now it only shows the standard switcher.