Is this a bug or a feature? Tracks display really small after lower screen editing

CB Pro 11, Windows 10.
I normally like to have all the tracks displayed as two lines high, so I can see all the buttons.
Quite often ill use a keyboard short cut to fit everything in to the main project window. This works fine. I see everything as large as possible in the one window.
Most of the time I use a lower screen editor, and nothing changes above, but when i close the editor all the tracks go really small, like one line small. Using my shortcut restores the window, but its a pain that the screen doesn’t go back to how it was, or in fact changes when i close the bottom window.
I’m sure its me, but cant figure out what i need to tick to stop this happening.