I've heard doubt is a big problem on the spiritual path. What does this text say about why a Guru is needed to overcome it?

According to the teachings in Chapter 50, a Guru is indispensable for removing doubt because ignorance itself manifests from doubt. The text warns that when doubt enters knowledge, even a very wise person can become prideful. It uses a powerful analogy, stating that doubt corrupts knowledge just as a single drop of fermented gruel ruins an entire pot of milk. Even a supreme knower like Shuka is said to have suffered loss due to doubt, highlighting that it cannot be removed without the guidance of a Guru, which is necessary to purify the mind.