One of the things lenders do in evaluating the risk of a potential borrower defaulting on a loan is to consider the potential borrower’s credit score.
Given that ...
In general, borrowers with higher credit scores are less likely to default on their loan.
Why is it that ...
For mortgage loans, the highest-credit-score borrowers default more often than other borrowers?
Goal
We'll need some sort of distinction about mortgage loans that could explain why high credit scores are associated with not being able to make your mortgage payments. (Maybe people with high credit scores are able to buy houses they can't actually afford)