bug with turbine

The space above and below the turbine are connected. There is nothing keeping the pressure below the turbine higher than the pressure above the turbine. The key to allow it to run is the difference between above and below pressures.

Oxygen is lighter than steam. He pushes the steam down. This schema worked for several dozen cycles until I noticed that it broke. Under the turbine is steam with a temperature above 300 degrees and a volume of 120 kilogram. The turbine should have been activated !!! If you go, break the turbine and build it again, it works again as expected. This is clearly a bug.