I'd always heard the sentence 'hung by the neck until dead' was taken literally: If you survived the drop, you're just gonna be hanging there longer. The result is the same.
The law/sentence was actually changed after a Scottish woman survived being hanged resulting in this specific wording. There was a time when people did survive and were freed.
I think there was a case somewhere that the prisoner was sentenced to death, and was executed ina fashion that didn't quite work.
But technically he did die for a minute or two before his heart restarted, and he sued to be released from prison because he technically served his sentence.
Unfortunately it doesn't look like it. I misremembered a few details, he "died" from natural causes in prison, not execution. The court ruled "Schreiber is either alive, in which case he must remain in prison, or he is dead, in which case this appeal is moot."