It’s good to encounter results you don’t expect. Isaac Asimov famously said:
The most exciting phrase to hear in science, the one that heralds new discoveries, is not “Eureka” but “That’s funny…”
As you gain more expertise, you become better at anticipating experimental or numerical outcomes. But at the same time, research is exploration, which I think means regularly encountering things that don’t initially make sense. You have to pay attention to the story told by the data, and sometimes your biased expectation gets in the way of you truly grasping what it’s saying. Accepting that the truth you seek runs deeper than your mental model of it is a healthy form of humility.
Unexpected results mean you actually stand to learn something new. The faster you learn to appreciate unexpected results—-instead of trying to force them into your existing paradigm—-the better. Especially pay attention to results that only seem slightly off—-I have gained significant insights from small deviations from my expectation that I initially assumed were inconsequential, but proved fascinating or important upon further reflection.