Toggle full-screen button not working to exit full-screen mode

[MeadowRunner]

When I am using the app in full screen, I can't use the toogle button to exit full-screen mode

1. Click on toggle full screen to make the app bigger.
2. View the app in full screen.
3. Click on "toggle full screen" at the top right.
4. Nothing happens.

I am able to leave full screen by pressing ESC instead.

I'm using Windows and Firefox.

[MeadowRunner]

I saw on the page of module 3 that this is a known issue in Firefox.