Typos catch the eye. Muddled words bring distraction. Mistakes do matter, but for the most part only because they’ll be one more thing on the list of corrections.
When you see them during your prep – because it is when rather than if for the majority of candidates – make a note in a useful way for you, then move past them. Focus on what matters more. Focus on the stuff that your examiners will really want to talk about: your contribution, your choices, your knowledge and what makes you a capable researcher.
Contribution matters more than corrections.