Here we go. My screen shot software struggles when I have to click on an image in QU!
Here the instaview is only a bit larger than the thumbnail and you can see my Raw has been refined with some extra fill
Here it is a bit larger than two thumbnails. The Raw has not been touched.
I have closed and re-opened QU to see if that sorted it. I have asked it to rebuild the thumbs.
Any clues?
What I did not do is to reload v120. I can do that the next time I go downstairs - and try any other fix you suggest!
EDIT. I have just looked on my other PC (the chunky slow one). It is the same. An instaview on an image where the RAW has not been touched is six inches tall. Where the RAW had been refined it is 3.5 inches tall. Sorry I cannot do screen shots as quickly as I can use a ruler!!
Tony