I also use this & I don't encounter your problem. If the water/milk is too hot, 漏奶 may happen because of the pressure being built up in the bottle. If this is not the case, you should go back to the shop & request an exchange.
489489,
I also used Chu Chu PPSU (the orange one) and Glass (The blue one) for 14 months la, I discover one time for your problem......then my husband discover that 當我洗完奶咀套番入個ring時套唔實!! Then, I try a again, the problem solved!! You can check check!!!