Instruct: Classify a given Amazon review into positive or negative sentiment.
Query: "First Months?"

We started using these roughly eight months ago. One of them didn't work intermittently from the beginning, and now the other is having problems. It appears to be an issue with how the contact for the batteries is made, so if you only used them on AC power this would not apply to you. They work just fine when they work, but when this little piece of metal in the battery compartment isn't making contact the unit won't work at all. Just a poor design.