Instruct: Classify Amazon reviews into positive or negative sentiment
Query: Faulty Unit, Be Aware for Bad Manufacturing

Unfortunately, as Garmin has expanded their quality control has been poor. While I believe this has the potential to be a good product, I purchased two of these units for my bike and my wife's. One of them came with an almost dead battery and a dead speed sensor (although the cadence works well). I am not the only person with this issue as the garmin support forums have had several people complain of this issue. Replacing the unit through G has been difficult as well. Their call center is slow and overwhelmed.The second unit works perfectly as expected, and provides what is advertised. The unit seamlessly pairs with both my forerunner 310xt and my wife's forerunner 405.So, while the product itself, if it worked w/o problem I would rate as a 4, the QC issues and issues with Garmin Customer Support make the GSC (which I am otherwise a fan of) a 2 star rating.