Bests & Worsts Reviews from Amazon

Upon arrival I would have rated this cup five stars all the way. It met all my requirements for a cup for my 18 month old; sturdy plastic that won't break, can't take the lid off or pull the straw out and make a mess and leak proof. Everything was fine until I noticed the tiny vent in the top of the lid had started to accumulate build up, just clean it right? Wrong. There's no way to clean it, I thought by pulling the silicone valve on the inner part of the lid would allow me to clean it but they only made things worse because there's no way to put that back in and now the cup leaks. Great cup while it lasted but the design of that vent on top of the lid is really bad unless someone can share how to clean it and how to insert than silicone thing back. I have attached pictures to give a visual of what I'm trying to say.