We too have the CCTV but it doesn't cover this: Pilot goes for a pee. Other pilot becomes incapacitated. Door entry system fails and we have an operational pilot in the cabin with the pax and unable to get back to the flight deck.
That's then about a tripple or quadruple failure. Door system has a fail safe mode, and if you know the code you can access from outside. If that's still not working, there is a general code and an emergency code. If you loose your captain (due to bladder leak) and you loose your FO and you loose all your electricity or the whole door mechanism - well that's less probable than an all engine failure I would say.
People always invent so complex failure when dealing with new systems. Come on - you can do better!
Dani