Tension is created when opposing perspectives meet, in the viva or elsewhere. In daily life that could be very challenging depending on the situation, but it doesn’t have to be that way in the viva.
Disagreement in the viva just means that there is something to talk about.
If there’s disagreement then the best thing you can do is explore why. What reasons do you or your examiners have for your positions or beliefs? What’s the evidence? What does that mean? Where do you have common ground and where do you really differ? And what does that mean?
A difference of opinion could mean simply understanding the other view. It could lead to an acknowledgment of an alternative in corrections to your thesis. It could be due to a simple mistake or error on someone’s part; discussion could help to resolve tension that’s purely accidental.
If you encounter disagreement in your viva, it may not be a big thing or a bad thing, but it’s something.
Something to talk about and resolve.