What milk do you usually buy?
Do you grab whatever is most popular at the supermarket?
I tend to select supermarket milk, full cream - I find the full cream milk will texture nicely compared to low fat, lite or A2 milk. If you're getting a lot of bubbles in your milk, try changing your milk brand, or style and see if it makes a difference. the Permeates in milk do affect the quality of steamed milk and the consistency.