What challenge did Das Ganu encounter while writing his commentary on the Ishavasya Upanishad, and what was Sai Baba's unusual advice for him as described in Chapter 20?

In Chapter 20, we learn that Das Ganu was writing a commentary called 'Ishavasya-Bhavartha-Bodhini' to make the Upanishad's meaning accessible. His challenge was that despite translating it word for word, he could not grasp the 'internal secret' or deep meaning, which left him feeling dissatisfied. When he presented this doubt to Sai Baba in Shirdi, Baba did not explain the scripture himself. Instead, as the chapter narrates, Baba told him that the resolution for his doubt would be provided by a maidservant at Kaka’s house when he returned there, demonstrating Baba's unique teaching methods.