I have a question and wondering if anyone is familiar with this problem. I have a Tamron 150-600 lens and have never been able to get an in focus photo with it. I use a Nikon D90 and D750. Both cameras were recently at Nikon and were repaired for different problems so I know that they are in good shape. The D750 for the warranty repair and the D90 for cleaning and check. Tamron currently has the lens for the 3rd time and they cannot recreate the problems I'm having. I cannot achieve focus at any focal length with either camera and the lens stopped communicating with both the last time I was testing after the second repair. I had the lens mounted on a sturdy tripod and tried manual focus, auto focus, VR was in the off position. Tamron replaced the mount during the second repair and it made no difference. They are asking me to send one of my cameras to see if the lens is slightly off and if so they can then adjust it to the camera. Their cameras all work fine. I am hesitate to send my camera to them but will if I must. If they adjust the lens to fit, for instance, the D90, then what are the chances that it will work with my D750? Also, both cameras work fine with my Nikon lenses and would be distressed if that changed after they had the camera. I find it odd that the lens is having trouble with both cameras. Does anyone have any advice or sent a camera to Tamron for a similar issue? I have used long lenses before so this isn't a new skill for me and I find this all very strange. I appreciate any help or advice.