Excessive leaking

I have the 120ml which doesn’t leak at all. I but the bigger bottles that I have leak badly. If make milk in them without the travel stopper it leaks. When I put the bottle in a little hot water to heat the milk up the milk rises through the system and leaks out the bottom entirely. I have to heat milk each time with the top off. The only way to stop it from leaking is by taking out the anti colic system which defeats the purpose of getting these bottles. Other than the leaking the anti- colic system really works. My baby is very gassy and it’s not hard to burp her as it happens within 5 minutes or just as I pick her up and burping has only become this easy since I started using these bottles. If they can fix the leaking issue these would get 5 star all the way