I would not assume your camera has a problem. More likely, there are some clouds, haze, the angle of the sun, or a similar factor affecting the level of light so that full sun in the situation you encountered is not Sunny 16.
The other three methods are pretty close - fractions of a stop apart. That seems to confirm correct metering and lower light than Sunny 16.
The JPEG images you posted do not have the EXIF data so I could not check for other issues. When you convert images for posting, it is helpful if you leave the EXIF data attached.