From the information you give us it’s tough to say Steve. There is so much that can go wrong with achieving AF that it could be a camera/lens issue, or pilot error.
The complexities of testing AF are covered well in two articles at lens rental by Roger Cicala. They can be found here and here . Phase Deteciton AF also works within a tolerable accuracy not a precise calibration. As such your 18-200 performance might well be different when mounted on your D7000 then when mounted on mine.
Perhaps a sample image showing the issue with the EXIF data intact will help us see what settings you are using, and what issues you are having.