Bests & Worsts Reviews from Amazon

I really like everything about this mug so I bought 2 more for other members of my family. They worked great for a while. But now a year later, 2 of the 3 have lost their vacuum and no longer keep beverages hot or cold for very long. So I figured it's just a manufacturing defect and they will replace. The problem is, they do not respond to warranty claims. Have filled out a claim form twice, including pictures and descriptions of the problem. I got an automated response telling me to wait 2-3 weeks for a reply. It's been over 2 months and have not heard anything. I tried emailing the warranty department directly, but the email bounced because the mailbox was full. Calling the toll free number results in a recorded message telling you to fill out the warranty claim form on their site - which is useless.