I purchased your product probably 1 year ago and it worked great. About 1 month ago my wife accidently dropped it and broke it. She went back to a W

I purchased your product probably 1 year ago and it worked great. About 1 month ago my wife accidently dropped it and broke it. She went back to a Walgreens in Omaha - where we had purchased it before - and got me a new one. I only used it about a week and the on off button quit working. My wife took it back to the Walgreens store and they exchanged it for a new one. Now this morning that one quit working having the same problem with the blue on off button. Can they have gotten a bad batch or do you think it is something I am doing? Have you had any problems with the on off buttons? I really like using it but dont want to have to keep taking it back.