1: Start a meeting
2: Click on full screen
3: Before the full screen page downloaded completely just close it,by close button on upper right corner of full screen.
4: In console Exit Full screen button will show not full screen.
5: We can go to full screen by restarting the meeting only.
6: Effect; if presenter selects full screen by mistake and clicked on the close button before the full screen has downloaded then he will not be able to go for full screen until he restarted the meeting again.