The milk contains big bubbles

Possible cause:
The milk is not cold enough or is not semi-skimmed.

We recommend using fresh, semi-skimmed or skimmed milk at refrigerator temperature (around 5°C).

Milk at this temperature is optimal for forming micro air bubbles, a prerequisite for obtaining a thick foam which also acts as a thermal insulator because it keeps the coffee and milk warm.

If the result is not as you wished, try changing brand of milk.