dcr66 wrote:

I tested it on Firefox today and it works.
However, I noticed that simply clicking the box is not enough, you have to select a move as well.
The process is like this:
1) You select a move to exit, and then press Move
2) The game appears again with a lot of warnings and the Exit Now! checkbox
3) You have to select again a move that does exit the map (this is critical, otherwise it won't work)
4) Check the "Exit Now!" checkbox
5) Press the Move button.
6) Your plan is now out of the game!
See image here: http://imgur.com/a/uYROXGZ

It has happened to me multiple times in the past that sometimes, I selected a move, sent it, and then when the game appeared again with the yellow warnings about exiting, I only checked the Exit Now! checkbox for confirmation and send again (thinking that I only had to confirm).
However, without selecting again the move, the Exit Now checkbox alone will not work (hence the impression that the system is broken).

@Chiggy Let me know if it works by following this steps, otherwise let me know which games you have trouble exiting and I will ask the webmaster to exit the game for you automatically (and debug them).