Look at the first statement of research in your thesis, your abstract. How clear is it? How would you explain it in plain, simple words? How would you remove jargon?
Would your abstract be enough to explain your ideas to a clever-but-less-knowledgeable person?
As a short viva prep exercise, consider writing a short UnAbstract. Something that doesn’t rely on specialist terms. Something that clearly states what you’ve done. It doesn’t mean you take each sentence of your abstract and simplify or de-jargon it. Use this opportunity this as a blank slate. Think about what your thesis actually does. Who is it for? Why would someone care about your research?
You’ve written thousands and thousands of words about your topic. Can you write a few more that are just plain, simple and clear about what you’ve done?