>As pointed out above, the EXIF data confirms that all three images were shot at infinity focus distance. I don't see AF >performance as an issue in this case. Some yes some no. The distance is said to be 7-8 miles. I have yet to get EXIF to show more than about 1 mile. The focus distance could be short relative to a 100% crop (which reduces the depth of field available by several stops) even though infinity is recorded. It makes good sense to start with the obvious - the target is about as close as it is possible to get for inaccurate AF - so try manual focus as a comparison
Photography is a bit like archery. A technically better camera, lens or arrow may not hit the target as often as it could if the photographer or archer does not practice enough.