Hello, Battleaxe.
For me, I think it has been in pretty clear situations of dark vs. light.
I think it may be something to do with distance-to-target, or shooting or attempting to shoot at things relatively close to me. I don't think I have had it occur during landscape type shots, it is more likely I see it during attempts to image closer objects.
Here is kind of what I am talking about. My riding chum "Herm" is wearing white or very light gray attire. His rather sleek racing hair cut (bald like me) is also reflecting a great deal of light.
But over half the shot or subject matter is within a shadow. The lens likely grabbed the nose of the bike as a focus point, as that seems is the about the sharpest spot in the image.
I think sometimes a situation like this might throw it off, or if I would have been standing in the shade shooting out of it, that also might have caused a stumble or reaction like you are having.
I think my experience like you are describing has been at distances-to-subject matter like this and CLOSER.
Just an idea-- maybe go find some intense shade vs. light and shoot some tests
into it and out of it?
Join to see EXIF info for this image (if available)
In the meantime, if and when I get out next I will certainly be watching for the same glitch you speak of and document the specifics of it, as I have seen it happen before.
~ Paul