Why game scene will automatically change to full screen

When i build and run my games in the PC/MAC standalone setting. It run according to what resolution i have set and in window mode (Window is set). But there is one scene, it will automatically change to full screen. Anyone know what is wrong? I tried to check the setting all those things, everything is the same. I don’t know why only one scene will automatically set to full screen?

Its 2014 and I’m having this same issue, no solution anywhere.

Its 2017 and I’m having this same issue, no solution anywhere.
Unity 2017.1.0f3

Same issue for me. Unity 2017.1.1

Oh, I also ran into this problem and just now found the answer myself.
Just press this button (watch screenshot)