Possible clue:
Jackson was said to have missed all but two or three of 45 rehearsals for the show but Patrick Woodroffe, a lighting engineer working at the LA arena, said that he had finally recovered some of his old magic in the past few days.
He told the BBC: “He came on stage at 9 o’clock in the evening and we all looked at each other and there was something that said that he really had it.
“Last night particularly, he came on stage and he was electric. It was like he had been holding back and suddenly he was performing as one had remembered him in the past.”
Perhaps he was in extra pain from that good, ie, strenuous, performance the night before.
And wanted an larger than usual dose of his daily demerol.
Thank Shermy. Sounds reasonable...