An update: this does NOT happen specifically when leaving the game. I today had the effect, but noticed in game at some time that the 4c was not responding any more. The whole report of “happens at the end of the game” was flawed. I just did not rely much on eye tracking during those game sessions (when traveling long distances and reading websites during the trip i tend to switch the device off) and did not notice the failure already during the gaming session. Only after leaving the game, i saw the error message.
Today while i was still using the decive in flight, it at some time (i keep switching it on and off, depending on what i do) the device did not start any more when it was switched off. When then leaving the game, i found the same error message as described above.