What specific problem did Das Ganu encounter while working on the Ishavasya Upanishad, and what was Sai Baba's unusual advice?

According to Chapter 20, Das Ganu was composing a commentary called the "Ishavasya-Bhavartha-Bodhini" to explain the Upanishad in simple Prakrit language. However, a doubt arose in his mind. Although he had translated the scripture word for word, he felt he could not grasp its "internal secret," which made the work joyless for him. When he took this doubt to Sai Baba in Shirdi, Baba gave him the perplexing advice that the resolution to his doubt would be provided by the maidservant at Kaka's house upon his return there.