my baby had this problem too when she was 5 months old. when she getting bigger she become lazy to suck the milk. then i change the 奶咀 to a bigger hole (but be careful on the first couple days baby may not get use to it) or did u release the ring of the 奶咀 when u feeding the baby? it's also easier for the baby to drink
Isaac_Ma, i think u can give it a try. just buy one to see see la. i think as long as his mouth is big enough to suck. will u boil and soak the new 奶咀 into the hot water for couple times before use? it can make the new 奶咀 softer. easier for him too