I've just recently seen this problem occur. It's been happening for 1 day now, I have not edited or done anything with Blockland, whenever I close the window, by pressing the Quit button, I disconnect from the internet, and I have to wait from 15-45 seconds for it to reconnect, it doesn't really take this long time(if I just manually disconnect and reconnect.)
It only happens when I close Blockland, and that's it.