In editor. F12; change editor color background to some color other than white.
Single document selected, multiple pages.
Shift to page View.
Change Zoom from 100% to 200%.
See your color background disappear.
Scroll down, scroll back up. The disappeared color area is smaller or gone, now. As you scroll the non-colored area off the screen, the color is restored when you page back to it – to the exact point you scrolled it off the screen.
Annoying.