Instruct: Classify Amazon reviews into positive or negative sentiment
Query: It works... but then it doesn't work

This bark collar works really well on my dog. It is a must have. BUT, the first one we purchased lasted about 16 months (not bad, I thought, I'll just buy a new one). I recently purchased a second collar and it leaked all over my dog on day one. Amazon was veary helpfull and they are replacing it for free. I hope this third collar is the one.