When I contacted Luv'ncare about my problems, they immediately emailed me with an address to send my cups back and they sent out a check within a couple of weeks. I've now owned about 60 of these things, so let me explain.
WHat many people don't realize is that the slits in the nipple sometimes tear, ever so slightly, causing the nipple to leak. ALSO, many kids clench the nipple between their teeth (much like a pacifer) without sucking, causing leaks. The nipple does bunch if over tightened and the caps sometimes twist crooked causing spillages. DISHWASHERS cause some kind of misshaping sometimes where the caps won't lock right, why I don't know, but it happens. Otherwise, my kids won't take anything else, so I continue to buy them. On vacation, my daughter lost her cup, we went to a local store who of course didn't carry them. SHe cried and fussed all night (lucky me)!