They're like this whether you have a valve or not, and temperature doesn't change when pumping out 5C air. It's not a visual bug, they simply are not working. I don't know if they're not working because they are overpressurized or whether there's two bugs interacting, but I can say with certainty that something is very wrong with the vent functionality.
I can even have air going _into_ a vent and just disappear, again not changing the gas composition or temperature at the output.