No, there don't seem to be any differences at 100%. The bug goes away at 66,6% and closer zoom. At 50% and less this effect alters my images and I can no longer edit them.
The difference between the two images is usually like a shadow of painting on a luminosity layer, e.g. If I had a luminosity layer with the curve to darken it, filled it with black, and painted a white circle (to darken the borders)... that would be the zone where the image would brighten after "merge visible", "flatten image", and "stamp visible".
The thing is I have never experienced anything like this. It just started an hour ago and forced me to quit working.
How can I make this thing disappear?
Would deleting the preference file by holding Command Option Shift at Photoshop startup help?