whitewolfowner wrote:
That is close to the situation I was shooting in. Aperture priority mode, anywhere from about 1/1600 to 1/800 of a second, medium ISO range around 200-400. Out of thousands of shots, it only did it when the Kenko was on and I tested multiple times. The teleconverter was the culprit, no doubt about it. Why, I do not know, but it caused the problem.
May be you got a bad apple, why don't you contact Kenko to address this problem. It may be caused by crossed circuit in the lens and caused short-circus. Send it back to Kenko for them to check it up, and you may get some compensation from them.