The text says even a wise person can suffer from doubt. What is the solution it offers to overcome this doubt and ignorance?

Chapter 50 emphasizes that doubt, or 'vikalpa,' is a serious obstacle, as it causes ignorance to manifest and can corrupt even a wise person's knowledge, just as a drop of fermented gruel can spoil a large pot of milk. The text is very clear about the solution: this ignorance, which is born from doubt, cannot be removed without a Guru. The role of the Guru is presented as essential for purifying the mind. By helping to remove doubt, the Guru facilitates the removal of ignorance, which is the necessary first step for the manifestation of infinite knowledge and the attainment of non-dual Samadhi.