The fat has begun to break down and there’s nothing you can do to make that steam any better.
One quick thing about fat that’s also worth noting is that fat affects flavor release in a drink
generally, milk foams better the further it is from its use by date because it’s the sort of breakdown of these fats that reduce its foam ability. And milk that foams badly or milk that has this issue, you’ll hear it almost fizz in the pitcher afterwards.