the way I believe it moves is this :
There are 2 tracks parallel to each other, connected by a turntable at each end.
You board the train in the same place you depart. Once boarded, the train moves down the track and ends on the first turntable. Whilst you are in the live action section, the train is turned round onto the return track. You then board the same train you were on and move back into the first room, onto the 2nd turntable. The train is then turned, with you still inside, back to the original starting position and you disembark.
This system can support up to 3 trains, which is what many people believe they are running. It would also explain that strange turning sensation at the end of the 2nd vr segment where you fall into the pit.
It explains the gas segment many people have been experiencing, as I would guess that this occurs when the train is on the turntable ready to move round, but there is another train on the other side of the turntable that needs to move off first.