for the "air air" 聲, you can put some vaseline on the 較位.
i have the same problem with the 星星 too! so annoying, i've changed to a new 星星 already but within a few days, it starts to 彈上去 again!! i think it must be the problem of the pump!!!
natalie,
are you using the 漏斗 now? is it really more powerful?? I read from some BK mami that the quantity of expressed milk decreases with the 漏斗...