How to maintain image position when switching between open files?

Sometimes I want to compare two open files in Photoshop. Often when I do this I make the images larger than the document window (meaning I would have to zoom out to make the image fit). I position the images such that will match when I switch between the two. <<< This used to work successfully.

Now when I attempt this and I switch away then back to a given image, the image has been re-positioned such that it docks one edge of the document window. I've searched in Preferences and on the web to no avail.

How can I set it to work as it used to?

Window 10, Photoshop CC

Thanks!