That’s super weird 
I can kinda get this to happen if:
- I hit the
Tabkey, which highlights the “Show Code” button - Then press the
Enterkey
But if I press any other key, then nothing happens.
Are you using the Google Chrome browser on Mac, Windows or Chromebook? Can you share your code? I can’t think of anyway that the code could be breaking 3DE like this, but maybe there’s something weird going on?
-Chris