I had a leak problem with a kid-size Kleen Kanteen 2 times - both user errors. First time I didn't get the sippy insert in all the way (what a mess!). Second time, I, uhm, learned, uhm, that you're not suppose to remove the inner rubber liner. I thought it was a packing piece or travel piece that need to be removed to get the liquid through the hole! Sure wish I didn't throw it out... Could it be anything similar?
