This version of the validator will not stop editing of the same record after saving.

validator-fixed-1

def validate_not_yet_responded
  has_responded = question.responses.any? do |r|
    r.chooser_id == self.chooser_id && r.id != self.id
  end
  if has_responded
    errors.add(:chooser_id, "you can only respond one time")
  end
end