macos – Command + Tab does not work as intended

I'm having trouble switching applications with CMD + TAB on my Macbook Pro (MacOS Mojave). Every now and then, when I use CMD + TAB and release the buttons when a desired application is highlighted. The system enters the viewfinder view, not the application.

This happens despite the fact that the applications are all maximized and should have their own view. I tried to Google this problem without luck.