I heard Sai Baba once got very angry when someone complained about how a devotee was massaging him. What happened exactly?

Yes, Chapter 24 recounts an incident where Sai Baba reacted with intense anger to criticism of a devotee's service. A lady was pressing Baba's stomach with what a great devotee perceived as excessive force. This devotee, filled with pity and worry, told the woman to have mercy and be more gentle, fearing she would break Baba's veins. Upon hearing these words, Baba's mood changed drastically. As mentioned in Chapter 24, he immediately rose, took his Satka, or short stick, and struck the ground with it. His eyes glowed like charcoal embers as he became terribly enraged, showing his displeasure with the interference in the devotee's loving service.