Hi,
I am experiencing this bug when i'm running in 1280x720 resolution. Whenever i go to system options in game and press "ok" the game turns to full screen. The only way to get back to windowed mode then is to get in and out of CashShop. The option "viewing mode" is not touched in system options. When pressing "windowed" it doesnt make any difference either. This only happens to me in 1280x720 resolution. When i switch to 800x600 resolution for example, this problem doesnt happen. I tried redownloading the game in a new folder and the same thing happens.