We do the same thing, and sometimes we end up interviewing somebody we thought we would not have to interview when something like this arises. At the end of the day, if there are conflicting versions, it's my role to determine, on the balance of probabilities, who is telling the truth and who isn't.
That's how it would happen in practice. It's not always easy. It's a difficult job, but that's essentially how we would solve it. It's by asking for additional documents, as you've mentioned, and by interviewing additional people. At the end of the day, I make a determination as to whom I believe and whom I don't believe.