leadbelly,
I tend to agree with you on the right side being way to soft.
However I'm just wondering if it might not be quite perfectly parallel to the wall.
If I was doing the test I'd also aim it a little to the left, and then to the right. And see how it changes the image.
Plus I don't have access to the Image Data. To me it looks like this shot was taken around the 16mm mark.
If it was how about trying it around 18 and 20mm. And see if the problems still exist.
I know that at that price a lens should be perfect. But the reality is that it's still a zoom, so there's usually a compromise in IQ on one end or the other
