My dear daughter also has the same problem. Till now we have yet to get a solution to it. I brought her to Kandang Kerbau Hospital last week to speak to a doc about it. Apparently, he said that since my dear daughter is gaining weight, there is no major problem. No fever, flu, cough or anything so he didnt do much test. It was basically a wasted trip for me. But I am also very worried about her constant regurgitation, it looks very uncomfortable and I worry that she will choke on her own milk.
But according to some old people, can try to give baby "jin feng san" to try to improve the situation. I will try it out today. Apply some on their gums before feeding them milk. Let me try a few days and let you know the outcome.