While scrolling up/down a page, the background image no longer flows smoothly like it used to. At least, I thought it used to.
The image to the left, of the robot and the person with the long hair and flowing cloak in desert now jumps and flickers when scrolling, moving with the page then snapping back into place. It was a slight annoyance at first, but it is getting to the point where it is bugging my eyes now and makes me want to do something else just because of the extra eye strain.
Thanks to @Michael Kjörling and @Molot I am providing more details:
I have found the same thing that Molot suggests in comments. It works fine in Internet Explorer (problem does not manifest there), but the problem exists in Edge. This explains why I used to be fine and recently noticed the change; I have been using Edge recently instead without even realizing I made the switch.
OS is Windows 10.
Also, because of the comment by Michael Kjörling I will update the post he linked to concerning the theme.