According to the EXIF data, the exposure and f/value are constant on the 4 photos. And the metering mode is "pattern" or "multi-segment" for all four shots (depending on the EXIF reader that I use).
So if they looked substantially different, there would be something wrong with our eyes, not our camera.
I don't know how to get your Canon to behave properly. But I do know that it's behaving consistently and identically (on those shots, at least) no matter what you did to it.
