Hegen bottle keeps leaking

My Hegen bottles keep leaking I can’t figure out why, anyone else face the same problem before? I’ve tried pressing down the teat cap one side at a time, pressing down both sides together at once with 2 hands but somehow milk still leaks out sometimes I have no idea why. When I close the cap, it feels like it has clicked in but sometimes it still leaks, is mine faulty or am I doing something wrong?