There are many controls that are not disabled upon opening a new window over Blockland in this new fullscreen.
Trying to type in a notepad document renders my team chat opening, my player painting, and my player jumping or crouching.
And I am required to click my windows button twice to come fully out of Blockland's window, otherwise it just flashes and goes straight back to Blockland.
edit: It would seem that the problem is more or less randomized, sometimes the Blockland window backgrounds completely, sometimes its half and half.
I really have to mess with the button to do it correctly.