Instruct: Classify Amazon reviews into positive or negative sentiment
Query: AUTO FOCUS LOCKS UP

The Auto-Focus feature of this lens started to lock-up after about 6 months. It was one of two Nikon lenses that I use. The other lens works fine. Sent it to Nikon for service 3 TIMES (yes 3) and each time they sent back the same lens and said nothing was wrong with it. After the 2nd return I went to my local camera shop to try a duplicate lens on my camera body, no problem. Pop on my original lens and it locks up after a few shots. Tried my lens on a another camera body in the store and it locks up on that body. Nikon does not stand by their warranty. This has dragged out over a period of two months and many phone calls. Nikon told me before sending the camera back for a 3rd time that they would replace the lens. They didn't. NIKON IS NOT THE COMPANY THEY USED TO BE.