I have noticed a few odd things.
When I have the toolbars hidden, and tap in center to bring up the bars, then visit the Formatting menu. When I then tap outside the menu, the top bar has moved down and the bottom bar has moved up. Both over a distance equal to their hight.
This does not reset and is cumulative on repeat. You can keep doing this until the bottom bar covers the top bar just about halfway down the page.
see image