I just spent the day making coffees for a work function. They hired an expobar commercial coffee machine and I failed to get one nice jug of milk all day, no matter what I tried it was always frothy with visible bubbles. I remember when I did my barista course I was doing great with milk texturing on various machines then was put on a machine which was doing something very similar to today. For anyone that uses these machines for a living, is there something that can cause this? Pressure too high perhaps? Or operator error? Although I doubt the last, I tried literally everything. I did notice it had a very small wand so I had trouble submerging it very far, but far enough that I was introducing air.
As far as I can see you are already experienced. Still, I can give a basic recipe that may help.
You should introduce hot air of course for bubbles and also to heat the milk up. Make circles with the wand inside the milk. Around 70 degrees Celsius is known to be good for heating milk for bubbles.
Then, you should stay on the surface. The wand should make some angle with the normal, so occasionally wand is in the thin surface of milk and air. There you can hear some hissing and whistling sound. Hearing the "paper tearing" sounds on the surface is important and told that they introduce micro bubbles.
Then, you can quickly (to not overheat) repeat these two to push the micro bubbles formed on the surface to the bottom of the jug and form new micro bubbles on the surface.
Do not forget to knock the jug to a massive wooden surface to push the liquid milk to the bottom and place the foam to the top of the jug after you finish.