Actually, NASA protocol requires more than a single layer of safety. The astronauts currently do not have a lifeboat home - that is extraordinarily irregular and I believe that it constitutes a danger to the astronauts. The spacecraft are not only for down transport, they are also shelters for radiation and particle events - which could be declared with days or hours notice. For a month these astronauts have had no viable shelter nor transport in case of emergency.

Danger is not when the last later of safety fails. Danger is when the level of risk exceeds a set threshold - and that level has been exceeded as per NASA protocol.