Problem with Oxygen Tank on ship losing contents.

I have and 'Oxygen Tank 1.5 m' directly mounted under my 'Cockpit 1.5 m', it is also connected to a 'Connector 1.5 m' from the small back port via a couple of 0.5 Conveyors. No O2 Gen or other tanks on board.

I set it to Charge while connected to my base and it fills as expected.

If I undock and then switch it Auto while still in the cockpit it starts hissing quite loudly and being used faster than I expect given that my suit O2 was filled while connected to the base. If I switch the tank back to Charge all contents vanish and it is now empty. The hissing continues until I redock and the noise switches back to filling sound.

If I fill the tank again, and then undock, if I then exit the cockpit, access the Control Panel via a port and switch the O2 tank to Auto while still out of the cockpit I can use the small O2 control on the front of the tank to fill my suit and it behaves as I would expect. If I re-enter the cockpit its starts hissing again, however if I exit the cockpit again it stops hissing and I can switch the tank back to Charge without losing the remaining gas.

Ship Blueprint in case it matters.