No, we don't redo everything.
We take the evidence and ask those drafting the report to explain the decisions they made and their reasoning. We take that and we look at it. Finally, we look at the decision, we determine whether it's okay, whether it's been adequately explained. If something is unclear or ambiguous, we can ask for it to be redone.
However, I feel that, in general, it's the same thing as when I was on the bench: When another person started the work, we had to ask ourselves whether there were questions of credibility or just questions of facts, reports, evidence, documents, and so on.
If the credibility isn't in question, we will continue what's already been started and render the decision. If the credibility is in question, we need to start over, because it's a personal matter. At the end of the day, it's my decision. I'm responsible for it. That means that I can't base myself on the testimony my predecessor received.