Looks like Murray's head has gone, it's a big part of his game. As the TV commentators have just said his head never affected his game when he was under Lendl. He needs to get it sorted out again and stop letting his head go in the middle of big matches.
He was at the start of the set, was it gamesmanship? Who knows, but if he was struggling he seems to have got over it now. Murray is in danger of his head going now though.