Yea, it's not that it was botched per se, it's just that this is a terrible, torturous way to execute someone.
N2 asphyxiation is only "peaceful" when it is an industrial accident or performed on a cooperative participant (i.e., self euthanasia) -- it just makes no sense for execution because someone who doesn't want to die is going to be tortured to death by it. Forced to fight every instinct they have to resist breathing until it hurts so bad they think they will die if they don't breath in, except they KNOW they'll die if they breath in so they push on.
It's really, really awful. It's a really horrendous way to execute.