How do you know your approach is a good one?
Is there only one way of interpreting your results?
Through years of study and focus, have you found one way of doing something, and now you only see that way of doing it?
Check your biases before the viva. Ask for your supervisor’s perspective. Ask if there were things that you discarded or which might be valuable. What have you ignored? What have you put to one side as you narrowed your focus?
You’re not looking for problems for the sake of it. You’re building certainty in the way you’ve done things, by being sure that you’ve not done something one way simply because you’re used to thinking of it that way.