Actually with the first two (the wheel), I started at 24mm infinity then walked away until the object filled approximately the same amt of the sensor at 40mm. It was not quite at infinity at 40mm, thus the room for accurate focus. The tree was shot all at infinity from the same location at 50mm with F2.8, F4, and F8. The tire was the only one that I moved the tripod for, and only the badly defocused shot was at infinity F2.8. I presented the two types of shot to provide clues as to what might be happening. Perhaps I confused the issue more than I clarified it.

At first, I had thought that the issue was just a focal length+aperture combination issue that might show up only at 24mm infinity. Then I took the 3 shots of the tree and found that even at 50mm infinity the same thing was happening at F2.8 especially. So from this, I gather that it is hitting the focus limiter before it reaches focus. So it's going back to KEH for repair.