Cannot maximize Apps from overview view on Xiaomi

After an undifined time, I cannot maximize Apps from the overview view (where one sees 4 miniature windows of active apps on the screen) on my Xiaomi Poco F7. I have to restart the phone, then it is working again.

I press the square to show active apps, tap on the app I want to maximize, mit nothing happens. I have to go back to the alphabet menu to select the app again to open it full screen