It’s clear that most PhD vivas results in success.
Ask your graduate school. Look online. Talk to people who have been through the process. The vast majority succeed. Corrections are part of the process and not a failure or setback. The process of doing a PhD, submitting a thesis and having a viva is not perfect, but it tends to work.
So accurately predicting success as the outcome of submission and the viva is simple.
Candidates succeed at the viva for very similar reasons, even when their research and theses could be very different. They succeed because they did the work, they wrote a good enough thesis and became a capable researcher. In the viva, they were able to demonstrate everything they needed to in order to pass.
Accurately predicting failure is much, much more challenging. Candidates pass for very similar reasons. They fail for very different, personal ones. It’s hard to know in advance.
Worry and nervousness isn’t enough. The vast majority of candidates succeed and most of them are in some way nervous about their viva! If you genuinely feel concerned that you’ve missed something or that something isn’t good enough, talk to someone. Talk to your supervisor. Talk to your graduate school. Talk to friends and colleagues and anyone who could help and ask them, “Do I really have a problem here? Am I just a little nervous? What can I do?”
Get help if your thoughts are turning to failure. It’s extremely unlikely, but finding a way that you can work towards success is much better than trying to assess how likely it is that you’re headed for failure.