I can recreate the issue on my machine. While playing in Fullscreen Windowed mode if I click on another monitor during a NPC Dialogue portion of the instance, it will disconnect me instantly. If I click another window while just standing in an instance, i don't get disconnected. It seems to be tied to the dialogue part of the instance since that's when I'm always being disconnected. Edit: Doesn't seem to happen while in Fullscreen mode. So far I can only recreate in "Fullscreen Windowed", haven't tested in just Windowed.