Confirm the authenticity of the mistake: First of all, please confirm that the problem you found is true, not misunderstanding or misreading. If the problem does exist, further confirm its importance.
Communication with the tutor: If you find mistakes in your doctoral thesis, you are advised to communicate with the doctoral tutor as soon as possible. They may be interested in your findings and make suggestions on how to deal with this problem.
Consult the literature: find out whether the mistake has been discovered or pointed out by others. If so, you may find that this problem has been discussed and explained in other documents.
Citation and reference: If you find a mistake in your doctoral thesis and need to mention it in your thesis, please make sure to quote and refer to the literature correctly. This helps to show that your research is based on a solid foundation and that you have a comprehensive understanding of related research.