Exit or cancel screen stuck...

[Thunderthud]

Had this occur at least three times on different Fire sticks, current HD Model and a 4k.

The box comes up with the blue highlight on exit. The the blue goes away and can't get that box off the screen. Can't exit the app but can go to Live and it runs under the Exit box.

Have to hit Home and force an HD app stop under app/settings.

Don't know what action causes this. Can't make it repeat at will.

Thanks