When opening a new page sometimes, there is an unused gap at the bottom, about 1/4". This started very recently. How do I get my displayed pages back to full size, and KEEP it there ?!? This is almost the same size as my bottom-of-screen taskbar, and in exactly that location. When the taskbar disappears, the unused space remains to annoy me and waste screen space.

I can temporarily fix this by pushing the middle display icon, but it just comes back later...

This is not full screen mode, it's the normal display using the full screen, including the bars and headings at the top.