thusband -ps: I don’t think the OPV functionality is your issue. It’s there to relief the pressure if necessary. I don’t think you are reading my sentences fully. 😊
Now that your connector is broken, it should be easy to see where the hissing is coming from. If ends in the drip tray via the outlet at the front, it has to come from the anti-vac valve, as any water from the OPV or steam from safety valve will leak into the machine via the broken outlet.