[Viewer]Problem: occasionally repeating pages

[millirem]

I'm using the latest Calibre on a Windows PC, and this problem has also existed in many prior versions of Calibre before the current one:

When reading an EPUB (repeatable across different books), and when I have configured the reader to show 2 pages on the screen at the same time (rather than the default 1 page), and when I have made no other reader config changes after resetting to defaults, AND when I have adjusted the size of the reader window away from the default (such as by maximizing the window): some pages will repeat themselves when I use PageUp/PageDown, as if I were instead using UpArrow/DownArrow.